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	$37.34	12.102%	$41.8589	$41.86	$41.85	$41.90
Purchase #2	$66.83	13.158%	$75.6235	$75.62	$75.60	$75.60
Purchase #3	$68.64	13.864%	$78.1562	$78.16	$78.15	$78.20
Purchase #4	$59.41	5.618%	$62.7477	$62.75	$62.75	$62.70
Purchase #5	$85.65	12.662%	$96.495	$96.50	$96.50	$96.50
Purchase #6	$89.28	9.396%	$97.6687	$97.67	$97.65	$97.70
Purchase #7	$195.37	7.124%	$209.2882	$209.29	$209.30	$209.30
7 purchase totals =	$602.52		$661.8382	$661.85	$661.80	$661.90