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	$36.82	11.737%	$41.1416	$41.14	$41.15	$41.10
Purchase #2	$70.34	10.129%	$77.4647	$77.46	$77.45	$77.50
Purchase #3	$39.44	5.129%	$41.4629	$41.46	$41.45	$41.50
Purchase #4	$191.60	3.156%	$197.6469	$197.65	$197.65	$197.60
Purchase #5	$82.41	7.401%	$88.5092	$88.51	$88.50	$88.50
Purchase #6	$141.82	7.204%	$152.0367	$152.04	$152.05	$152.00
Purchase #7	$97.75	7.482%	$105.0637	$105.06	$105.05	$105.10
7 purchase totals =	$660.18		$703.3257	$703.32	$703.30	$703.30