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	$171.76	7.201%	$184.1284	$184.13	$184.15	$184.10
Purchase #2	$246.81	5.128%	$259.4664	$259.47	$259.45	$259.50
Purchase #3	$169.54	8.677%	$184.251	$184.25	$184.25	$184.30
Purchase #4	$34.54	8.704%	$37.5464	$37.55	$37.55	$37.50
Purchase #5	$79.73	11.472%	$88.8766	$88.88	$88.90	$88.90
Purchase #6	$178.63	3.311%	$184.5444	$184.54	$184.55	$184.50
Purchase #7	$64.91	9.556%	$71.1128	$71.11	$71.10	$71.10
7 purchase totals =	$945.92		$1,009.9260	$1,009.93	$1,009.95	$1,009.90