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	$139.71	10.208%	$153.9716	$153.97	$153.95	$154.00
Purchase #2	$95.47	4.619%	$99.8798	$99.88	$99.90	$99.90
Purchase #3	$196.56	13.427%	$222.9521	$222.95	$222.95	$223.00
Purchase #4	$172.86	10.753%	$191.4476	$191.45	$191.45	$191.40
Purchase #5	$242.69	12.568%	$273.1913	$273.19	$273.20	$273.20
Purchase #6	$247.75	6.560%	$264.0024	$264.00	$264.00	$264.00
Purchase #7	$220.82	10.830%	$244.7348	$244.73	$244.75	$244.70
7 purchase totals =	$1,315.86		$1,450.1796	$1,450.17	$1,450.20	$1,450.20