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	$64.98	8.666%	$70.6112	$70.61	$70.60	$70.60
Purchase #2	$133.41	13.502%	$151.423	$151.42	$151.40	$151.40
Purchase #3	$191.98	4.791%	$201.1778	$201.18	$201.20	$201.20
Purchase #4	$232.36	5.142%	$244.308	$244.31	$244.30	$244.30
Purchase #5	$191.46	10.446%	$211.4599	$211.46	$211.45	$211.50
Purchase #6	$92.98	10.729%	$102.9558	$102.96	$102.95	$103.00
Purchase #7	$74.66	6.445%	$79.4718	$79.47	$79.45	$79.50
7 purchase totals =	$981.83		$1,061.4075	$1,061.41	$1,061.35	$1,061.50