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	$92.89	3.538%	$96.1764	$96.18	$96.20	$96.20
Purchase #2	$156.87	11.379%	$174.7202	$174.72	$174.70	$174.70
Purchase #3	$129.42	7.717%	$139.4073	$139.41	$139.40	$139.40
Purchase #4	$55.48	7.624%	$59.7098	$59.71	$59.70	$59.70
Purchase #5	$110.81	3.300%	$114.4667	$114.47	$114.45	$114.50
Purchase #6	$182.79	5.232%	$192.3536	$192.35	$192.35	$192.40
Purchase #7	$222.68	4.643%	$233.019	$233.02	$233.00	$233.00
7 purchase totals =	$950.94		$1,009.8530	$1,009.86	$1,009.80	$1,009.90