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	$155.32	6.398%	$165.2574	$165.26	$165.25	$165.30
Purchase #2	$184.84	10.126%	$203.5569	$203.56	$203.55	$203.60
Purchase #3	$204.40	6.373%	$217.4264	$217.43	$217.45	$217.40
Purchase #4	$89.69	10.454%	$99.0662	$99.07	$99.05	$99.10
Purchase #5	$209.98	9.629%	$230.199	$230.20	$230.20	$230.20
Purchase #6	$67.34	11.169%	$74.8612	$74.86	$74.85	$74.90
Purchase #7	$67.41	7.182%	$72.2514	$72.25	$72.25	$72.30
7 purchase totals =	$978.98		$1,062.6185	$1,062.63	$1,062.60	$1,062.80