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	$165.88	13.118%	$187.6401	$187.64	$187.65	$187.60
Purchase #2	$192.99	12.136%	$216.4113	$216.41	$216.40	$216.40
Purchase #3	$135.59	5.142%	$142.562	$142.56	$142.55	$142.60
Purchase #4	$127.25	8.281%	$137.7876	$137.79	$137.80	$137.80
Purchase #5	$143.31	4.816%	$150.2118	$150.21	$150.20	$150.20
Purchase #6	$143.78	3.219%	$148.4083	$148.41	$148.40	$148.40
Purchase #7	$17.25	11.764%	$19.2793	$19.28	$19.30	$19.30
7 purchase totals =	$926.05		$1,002.3004	$1,002.30	$1,002.30	$1,002.30