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	$41.31	13.111%	$46.7262	$46.73	$46.75	$46.70
Purchase #2	$156.76	9.850%	$172.2009	$172.20	$172.20	$172.20
Purchase #3	$64.49	11.533%	$71.9276	$71.93	$71.95	$71.90
Purchase #4	$165.35	11.639%	$184.5951	$184.60	$184.60	$184.60
Purchase #5	$68.57	4.440%	$71.6145	$71.61	$71.60	$71.60
Purchase #6	$196.30	7.577%	$211.1737	$211.17	$211.15	$211.20
Purchase #7	$79.91	8.787%	$86.9317	$86.93	$86.95	$86.90
7 purchase totals =	$772.69		$845.1697	$845.17	$845.20	$845.10