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	$77.45	4.486%	$80.9244	$80.92	$80.90	$80.90
Purchase #2	$101.48	4.767%	$106.3176	$106.32	$106.30	$106.30
Purchase #3	$85.86	12.515%	$96.6054	$96.61	$96.60	$96.60
Purchase #4	$13.61	3.342%	$14.0648	$14.06	$14.05	$14.10
Purchase #5	$111.66	11.345%	$124.3278	$124.33	$124.35	$124.30
Purchase #6	$54.52	8.753%	$59.2921	$59.29	$59.30	$59.30
Purchase #7	$192.25	13.307%	$217.8327	$217.83	$217.85	$217.80
7 purchase totals =	$636.83		$699.3648	$699.36	$699.35	$699.30