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	$100.89	13.614%	$114.6252	$114.63	$114.65	$114.60
Purchase #2	$219.37	6.284%	$233.1552	$233.16	$233.15	$233.20
Purchase #3	$181.92	10.120%	$200.3303	$200.33	$200.35	$200.30
Purchase #4	$102.41	6.596%	$109.165	$109.17	$109.15	$109.20
Purchase #5	$227.64	7.824%	$245.4506	$245.45	$245.45	$245.50
Purchase #6	$117.65	11.428%	$131.095	$131.10	$131.10	$131.10
Purchase #7	$96.39	5.402%	$101.597	$101.60	$101.60	$101.60
7 purchase totals =	$1,046.27		$1,135.4183	$1,135.44	$1,135.45	$1,135.50