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	$184.38	3.131%	$190.1529	$190.15	$190.15	$190.20
Purchase #2	$31.50	7.313%	$33.8036	$33.80	$33.80	$33.80
Purchase #3	$53.87	5.593%	$56.8829	$56.88	$56.90	$56.90
Purchase #4	$59.66	7.635%	$64.215	$64.22	$64.20	$64.20
Purchase #5	$95.95	8.309%	$103.9225	$103.92	$103.90	$103.90
Purchase #6	$73.31	4.437%	$76.5628	$76.56	$76.55	$76.60
Purchase #7	$189.35	12.637%	$213.2782	$213.28	$213.30	$213.30
7 purchase totals =	$688.02		$738.8179	$738.81	$738.80	$738.90