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	$73.32	6.593%	$78.154	$78.15	$78.15	$78.20
Purchase #2	$53.95	13.502%	$61.2343	$61.23	$61.25	$61.20
Purchase #3	$125.38	4.671%	$131.2365	$131.24	$131.25	$131.20
Purchase #4	$130.89	4.772%	$137.1361	$137.14	$137.15	$137.10
Purchase #5	$70.89	9.217%	$77.4239	$77.42	$77.40	$77.40
Purchase #6	$207.47	4.519%	$216.8456	$216.85	$216.85	$216.80
Purchase #7	$28.80	5.323%	$30.333	$30.33	$30.35	$30.30
7 purchase totals =	$690.70		$732.3634	$732.36	$732.40	$732.20