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	$90.50	4.576%	$94.6413	$94.64	$94.65	$94.60
Purchase #2	$79.50	4.823%	$83.3343	$83.33	$83.35	$83.30
Purchase #3	$76.41	6.840%	$81.6364	$81.64	$81.65	$81.60
Purchase #4	$147.32	3.463%	$152.4217	$152.42	$152.40	$152.40
Purchase #5	$55.66	6.629%	$59.3497	$59.35	$59.35	$59.30
Purchase #6	$151.82	9.499%	$166.2414	$166.24	$166.25	$166.20
Purchase #7	$144.50	8.540%	$156.8403	$156.84	$156.85	$156.80
7 purchase totals =	$745.71		$794.4651	$794.46	$794.50	$794.20