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	$36.41	13.720%	$41.4055	$41.41	$41.40	$41.40
Purchase #2	$165.76	9.678%	$181.8023	$181.80	$181.80	$181.80
Purchase #3	$28.72	5.557%	$30.316	$30.32	$30.30	$30.30
Purchase #4	$145.42	3.813%	$150.9649	$150.96	$150.95	$151.00
Purchase #5	$162.98	5.632%	$172.159	$172.16	$172.15	$172.20
Purchase #6	$39.35	12.501%	$44.2691	$44.27	$44.25	$44.30
Purchase #7	$101.95	10.700%	$112.8587	$112.86	$112.85	$112.90
7 purchase totals =	$680.59		$733.7755	$733.78	$733.70	$733.90