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	$198.85	9.846%	$218.4288	$218.43	$218.45	$218.40
Purchase #2	$142.50	11.723%	$159.2053	$159.21	$159.20	$159.20
Purchase #3	$68.33	10.196%	$75.2969	$75.30	$75.30	$75.30
Purchase #4	$201.59	12.549%	$226.8875	$226.89	$226.90	$226.90
Purchase #5	$162.37	11.634%	$181.2601	$181.26	$181.25	$181.30
Purchase #6	$119.73	7.113%	$128.2464	$128.25	$128.25	$128.20
Purchase #7	$67.84	6.331%	$72.135	$72.14	$72.15	$72.10
7 purchase totals =	$961.21		$1,061.4600	$1,061.48	$1,061.50	$1,061.40