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	$73.30	13.441%	$83.1523	$83.15	$83.15	$83.20
Purchase #2	$78.51	13.782%	$89.3302	$89.33	$89.35	$89.30
Purchase #3	$91.90	13.601%	$104.3993	$104.40	$104.40	$104.40
Purchase #4	$47.98	11.221%	$53.3638	$53.36	$53.35	$53.40
Purchase #5	$165.57	13.796%	$188.412	$188.41	$188.40	$188.40
Purchase #6	$93.70	11.319%	$104.3059	$104.31	$104.30	$104.30
Purchase #7	$91.85	5.135%	$96.5665	$96.57	$96.55	$96.60
7 purchase totals =	$642.81		$719.5300	$719.53	$719.50	$719.60