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	$36.36	4.246%	$37.9038	$37.90	$37.90	$37.90
Purchase #2	$199.30	10.761%	$220.7467	$220.75	$220.75	$220.70
Purchase #3	$208.82	6.385%	$222.1532	$222.15	$222.15	$222.20
Purchase #4	$198.50	6.550%	$211.5018	$211.50	$211.50	$211.50
Purchase #5	$215.58	8.465%	$233.8288	$233.83	$233.85	$233.80
Purchase #6	$242.88	11.604%	$271.0638	$271.06	$271.05	$271.10
Purchase #7	$130.91	4.148%	$136.3401	$136.34	$136.35	$136.30
7 purchase totals =	$1,232.35		$1,333.5382	$1,333.53	$1,333.55	$1,333.50