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	$200.80	7.541%	$215.9423	$215.94	$215.95	$215.90
Purchase #2	$17.46	7.812%	$18.824	$18.82	$18.80	$18.80
Purchase #3	$11.89	10.560%	$13.1456	$13.15	$13.15	$13.10
Purchase #4	$89.97	7.832%	$97.0165	$97.02	$97.00	$97.00
Purchase #5	$215.53	5.496%	$227.3755	$227.38	$227.40	$227.40
Purchase #6	$71.89	5.412%	$75.7807	$75.78	$75.80	$75.80
Purchase #7	$39.79	13.197%	$45.0411	$45.04	$45.05	$45.00
7 purchase totals =	$647.33		$693.1257	$693.13	$693.15	$693.00