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	$188.34	9.198%	$205.6635	$205.66	$205.65	$205.70
Purchase #2	$119.27	3.315%	$123.2238	$123.22	$123.20	$123.20
Purchase #3	$82.59	9.104%	$90.109	$90.11	$90.10	$90.10
Purchase #4	$93.33	6.202%	$99.1183	$99.12	$99.10	$99.10
Purchase #5	$103.52	10.781%	$114.6805	$114.68	$114.70	$114.70
Purchase #6	$124.39	3.676%	$128.9626	$128.96	$128.95	$129.00
Purchase #7	$183.43	3.530%	$189.9051	$189.91	$189.90	$189.90
7 purchase totals =	$894.87		$951.6628	$951.66	$951.60	$951.70