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	$89.36	13.392%	$101.3271	$101.33	$101.35	$101.30
Purchase #2	$49.26	5.733%	$52.0841	$52.08	$52.10	$52.10
Purchase #3	$17.71	5.227%	$18.6357	$18.64	$18.65	$18.60
Purchase #4	$78.77	13.662%	$89.5316	$89.53	$89.55	$89.50
Purchase #5	$197.52	7.393%	$212.1227	$212.12	$212.10	$212.10
Purchase #6	$212.59	3.548%	$220.1327	$220.13	$220.15	$220.10
Purchase #7	$19.57	9.303%	$21.3906	$21.39	$21.40	$21.40
7 purchase totals =	$664.78		$715.2245	$715.22	$715.30	$715.10