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	$107.26	3.733%	$111.264	$111.26	$111.25	$111.30
Purchase #2	$200.69	13.687%	$228.1584	$228.16	$228.15	$228.20
Purchase #3	$240.46	10.370%	$265.3957	$265.40	$265.40	$265.40
Purchase #4	$52.53	4.533%	$54.9112	$54.91	$54.90	$54.90
Purchase #5	$198.79	11.324%	$221.301	$221.30	$221.30	$221.30
Purchase #6	$106.27	5.570%	$112.1892	$112.19	$112.20	$112.20
Purchase #7	$82.41	7.219%	$88.3592	$88.36	$88.35	$88.40
7 purchase totals =	$988.41		$1,081.5787	$1,081.58	$1,081.55	$1,081.70