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	$230.41	9.812%	$253.0178	$253.02	$253.00	$253.00
Purchase #2	$50.88	8.712%	$55.3127	$55.31	$55.30	$55.30
Purchase #3	$156.59	5.498%	$165.1993	$165.20	$165.20	$165.20
Purchase #4	$207.73	7.459%	$223.2246	$223.22	$223.20	$223.20
Purchase #5	$70.29	9.199%	$76.756	$76.76	$76.75	$76.80
Purchase #6	$199.85	8.375%	$216.5874	$216.59	$216.60	$216.60
Purchase #7	$11.74	9.742%	$12.8837	$12.88	$12.90	$12.90
7 purchase totals =	$927.49		$1,002.9815	$1,002.98	$1,002.95	$1,003.00