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	$118.49	5.218%	$124.6728	$124.67	$124.65	$124.70
Purchase #2	$179.30	13.486%	$203.4804	$203.48	$203.50	$203.50
Purchase #3	$152.36	13.510%	$172.9438	$172.94	$172.95	$172.90
Purchase #4	$72.82	13.488%	$82.642	$82.64	$82.65	$82.60
Purchase #5	$96.73	12.216%	$108.5465	$108.55	$108.55	$108.50
Purchase #6	$188.45	3.173%	$194.4295	$194.43	$194.45	$194.40
Purchase #7	$233.83	3.635%	$242.3297	$242.33	$242.35	$242.30
7 purchase totals =	$1,041.98		$1,129.0447	$1,129.04	$1,129.10	$1,128.90