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	$195.59	13.746%	$222.4758	$222.48	$222.50	$222.50
Purchase #2	$211.44	6.479%	$225.1392	$225.14	$225.15	$225.10
Purchase #3	$55.98	7.670%	$60.2737	$60.27	$60.25	$60.30
Purchase #4	$155.84	6.385%	$165.7904	$165.79	$165.80	$165.80
Purchase #5	$121.64	7.838%	$131.1741	$131.17	$131.15	$131.20
Purchase #6	$52.49	5.253%	$55.2473	$55.25	$55.25	$55.20
Purchase #7	$173.31	13.851%	$197.3152	$197.32	$197.30	$197.30
7 purchase totals =	$966.29		$1,057.4157	$1,057.42	$1,057.40	$1,057.40