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	$172.64	5.244%	$181.6932	$181.69	$181.70	$181.70
Purchase #2	$199.57	5.428%	$210.4027	$210.40	$210.40	$210.40
Purchase #3	$123.64	3.194%	$127.5891	$127.59	$127.60	$127.60
Purchase #4	$242.35	6.344%	$257.7247	$257.72	$257.70	$257.70
Purchase #5	$37.62	8.512%	$40.8222	$40.82	$40.80	$40.80
Purchase #6	$152.78	9.454%	$167.2238	$167.22	$167.20	$167.20
Purchase #7	$74.97	8.757%	$81.5351	$81.54	$81.55	$81.50
7 purchase totals =	$1,003.57		$1,066.9908	$1,066.98	$1,066.95	$1,066.90