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	$114.54	13.595%	$130.1117	$130.11	$130.10	$130.10
Purchase #2	$174.98	6.108%	$185.6678	$185.67	$185.65	$185.70
Purchase #3	$93.92	12.124%	$105.3069	$105.31	$105.30	$105.30
Purchase #4	$194.67	4.421%	$203.2764	$203.28	$203.30	$203.30
Purchase #5	$43.33	4.834%	$45.4246	$45.42	$45.40	$45.40
Purchase #6	$250.97	6.538%	$267.3784	$267.38	$267.40	$267.40
Purchase #7	$7.31	5.166%	$7.6876	$7.69	$7.70	$7.70
7 purchase totals =	$879.72		$944.8534	$944.86	$944.85	$944.90