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	$79.29	7.480%	$85.2209	$85.22	$85.20	$85.20
Purchase #2	$88.72	7.442%	$95.3225	$95.32	$95.30	$95.30
Purchase #3	$245.41	9.414%	$268.5129	$268.51	$268.50	$268.50
Purchase #4	$233.93	3.767%	$242.7421	$242.74	$242.75	$242.70
Purchase #5	$41.90	9.444%	$45.857	$45.86	$45.85	$45.90
Purchase #6	$57.34	4.217%	$59.758	$59.76	$59.75	$59.80
Purchase #7	$232.55	3.341%	$240.3195	$240.32	$240.30	$240.30
7 purchase totals =	$979.14		$1,037.7329	$1,037.73	$1,037.65	$1,037.70