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	$99.71	9.769%	$109.4507	$109.45	$109.45	$109.50
Purchase #2	$207.91	11.304%	$231.4121	$231.41	$231.40	$231.40
Purchase #3	$218.43	13.505%	$247.929	$247.93	$247.95	$247.90
Purchase #4	$40.34	13.751%	$45.8872	$45.89	$45.90	$45.90
Purchase #5	$240.63	9.818%	$264.2551	$264.26	$264.25	$264.30
Purchase #6	$107.59	13.740%	$122.3729	$122.37	$122.35	$122.40
Purchase #7	$38.61	8.576%	$41.9212	$41.92	$41.90	$41.90
7 purchase totals =	$953.22		$1,063.2282	$1,063.23	$1,063.20	$1,063.30