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	$201.80	11.537%	$225.0817	$225.08	$225.10	$225.10
Purchase #2	$223.25	9.103%	$243.5724	$243.57	$243.55	$243.60
Purchase #3	$83.67	9.263%	$91.4204	$91.42	$91.40	$91.40
Purchase #4	$84.99	13.131%	$96.15	$96.15	$96.15	$96.20
Purchase #5	$172.49	7.205%	$184.9179	$184.92	$184.90	$184.90
Purchase #6	$51.61	13.181%	$58.4127	$58.41	$58.40	$58.40
Purchase #7	$190.40	3.112%	$196.3252	$196.33	$196.35	$196.30
7 purchase totals =	$1,008.21		$1,095.8803	$1,095.88	$1,095.85	$1,095.90