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	$178.41	11.742%	$199.3589	$199.36	$199.35	$199.40
Purchase #2	$173.59	8.834%	$188.9249	$188.92	$188.90	$188.90
Purchase #3	$68.71	13.361%	$77.8903	$77.89	$77.90	$77.90
Purchase #4	$222.53	12.551%	$250.4597	$250.46	$250.45	$250.50
Purchase #5	$207.66	12.570%	$233.7629	$233.76	$233.75	$233.80
Purchase #6	$167.48	3.777%	$173.8057	$173.81	$173.80	$173.80
Purchase #7	$53.29	11.265%	$59.2931	$59.29	$59.30	$59.30
7 purchase totals =	$1,071.67		$1,183.4955	$1,183.49	$1,183.45	$1,183.60