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	$229.35	5.572%	$242.1294	$242.13	$242.15	$242.10
Purchase #2	$68.95	3.155%	$71.1254	$71.13	$71.15	$71.10
Purchase #3	$232.99	12.103%	$261.1888	$261.19	$261.20	$261.20
Purchase #4	$64.88	10.843%	$71.9149	$71.91	$71.90	$71.90
Purchase #5	$207.50	11.486%	$231.3335	$231.33	$231.35	$231.30
Purchase #6	$120.38	13.156%	$136.2172	$136.22	$136.20	$136.20
Purchase #7	$42.77	12.152%	$47.9674	$47.97	$47.95	$48.00
7 purchase totals =	$966.82		$1,061.8766	$1,061.88	$1,061.90	$1,061.80