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	$122.34	3.174%	$126.2231	$126.22	$126.20	$126.20
Purchase #2	$6.36	5.177%	$6.6893	$6.69	$6.70	$6.70
Purchase #3	$142.27	5.724%	$150.4135	$150.41	$150.40	$150.40
Purchase #4	$122.58	3.873%	$127.3275	$127.33	$127.35	$127.30
Purchase #5	$222.69	4.701%	$233.1587	$233.16	$233.15	$233.20
Purchase #6	$88.57	12.705%	$99.8228	$99.82	$99.80	$99.80
Purchase #7	$65.97	7.762%	$71.0906	$71.09	$71.10	$71.10
7 purchase totals =	$770.78		$814.7255	$814.72	$814.70	$814.70