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	$162.80	5.259%	$171.3617	$171.36	$171.35	$171.40
Purchase #2	$25.95	12.363%	$29.1582	$29.16	$29.15	$29.20
Purchase #3	$80.69	11.472%	$89.9468	$89.95	$89.95	$89.90
Purchase #4	$133.51	9.673%	$146.4244	$146.42	$146.40	$146.40
Purchase #5	$81.55	8.871%	$88.7843	$88.78	$88.80	$88.80
Purchase #6	$111.86	8.541%	$121.414	$121.41	$121.40	$121.40
Purchase #7	$71.40	9.608%	$78.2601	$78.26	$78.25	$78.30
7 purchase totals =	$667.76		$725.3495	$725.34	$725.30	$725.40