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	$115.27	10.476%	$127.3457	$127.35	$127.35	$127.30
Purchase #2	$245.44	13.769%	$279.2346	$279.23	$279.25	$279.20
Purchase #3	$133.44	11.830%	$149.226	$149.23	$149.25	$149.20
Purchase #4	$73.48	13.108%	$83.1118	$83.11	$83.10	$83.10
Purchase #5	$59.57	13.785%	$67.7817	$67.78	$67.80	$67.80
Purchase #6	$54.34	9.375%	$59.4344	$59.43	$59.45	$59.40
Purchase #7	$46.82	11.693%	$52.2947	$52.29	$52.30	$52.30
7 purchase totals =	$728.36		$818.4289	$818.42	$818.50	$818.30