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	$89.52	10.439%	$98.865	$98.87	$98.85	$98.90
Purchase #2	$134.98	13.744%	$153.5317	$153.53	$153.55	$153.50
Purchase #3	$122.31	4.348%	$127.628	$127.63	$127.65	$127.60
Purchase #4	$194.29	11.287%	$216.2195	$216.22	$216.20	$216.20
Purchase #5	$42.77	7.198%	$45.8486	$45.85	$45.85	$45.80
Purchase #6	$88.79	10.773%	$98.3553	$98.36	$98.35	$98.40
Purchase #7	$44.65	9.364%	$48.831	$48.83	$48.85	$48.80
7 purchase totals =	$717.31		$789.2791	$789.29	$789.30	$789.20