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	$90.61	5.142%	$95.2692	$95.27	$95.25	$95.30
Purchase #2	$155.37	8.544%	$168.6448	$168.64	$168.65	$168.60
Purchase #3	$25.37	11.677%	$28.3325	$28.33	$28.35	$28.30
Purchase #4	$236.52	9.862%	$259.8456	$259.85	$259.85	$259.80
Purchase #5	$129.29	9.720%	$141.857	$141.86	$141.85	$141.90
Purchase #6	$113.92	11.441%	$126.9536	$126.95	$126.95	$127.00
Purchase #7	$210.71	3.722%	$218.5526	$218.55	$218.55	$218.60
7 purchase totals =	$961.79		$1,039.4553	$1,039.45	$1,039.45	$1,039.50