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	$59.56	3.400%	$61.585	$61.59	$61.60	$61.60
Purchase #2	$68.85	3.424%	$71.2074	$71.21	$71.20	$71.20
Purchase #3	$116.84	12.239%	$131.14	$131.14	$131.15	$131.10
Purchase #4	$53.48	11.155%	$59.4457	$59.45	$59.45	$59.40
Purchase #5	$188.33	4.530%	$196.8613	$196.86	$196.85	$196.90
Purchase #6	$66.53	3.869%	$69.104	$69.10	$69.10	$69.10
Purchase #7	$9.90	6.613%	$10.5547	$10.55	$10.55	$10.60
7 purchase totals =	$563.49		$599.8981	$599.90	$599.90	$599.90