Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.86	5.280%	$141.9806	$141.98	$142.00	$142.00
Purchase #2	$131.39	11.230%	$146.1451	$146.15	$146.15	$146.10
Purchase #3	$145.49	13.774%	$165.5298	$165.53	$165.55	$165.50
Purchase #4	$227.37	9.210%	$248.3108	$248.31	$248.30	$248.30
Purchase #5	$172.56	5.382%	$181.8472	$181.85	$181.85	$181.80
Purchase #6	$202.57	13.731%	$230.3849	$230.38	$230.40	$230.40
Purchase #7	$170.96	9.396%	$187.0234	$187.02	$187.00	$187.00
7 purchase totals =	$1,185.20		$1,301.2218	$1,301.22	$1,301.25	$1,301.10