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	$63.93	12.140%	$71.6911	$71.69	$71.70	$71.70
Purchase #2	$168.76	12.325%	$189.5597	$189.56	$189.55	$189.60
Purchase #3	$61.74	5.357%	$65.0474	$65.05	$65.05	$65.00
Purchase #4	$110.38	7.588%	$118.7556	$118.76	$118.75	$118.80
Purchase #5	$31.29	8.329%	$33.8961	$33.90	$33.90	$33.90
Purchase #6	$234.64	12.418%	$263.7776	$263.78	$263.80	$263.80
Purchase #7	$215.72	8.195%	$233.3983	$233.40	$233.40	$233.40
7 purchase totals =	$886.46		$976.1258	$976.14	$976.15	$976.20