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	$149.25	12.658%	$168.1421	$168.14	$168.15	$168.10
Purchase #2	$168.89	9.633%	$185.1592	$185.16	$185.15	$185.20
Purchase #3	$249.96	5.656%	$264.0977	$264.10	$264.10	$264.10
Purchase #4	$50.53	4.719%	$52.9145	$52.91	$52.90	$52.90
Purchase #5	$116.79	10.336%	$128.8614	$128.86	$128.85	$128.90
Purchase #6	$156.63	3.252%	$161.7236	$161.72	$161.70	$161.70
Purchase #7	$67.75	4.299%	$70.6626	$70.66	$70.65	$70.70
7 purchase totals =	$959.80		$1,031.5611	$1,031.55	$1,031.50	$1,031.60