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	$156.29	5.852%	$165.4361	$165.44	$165.45	$165.40
Purchase #2	$138.79	11.847%	$155.2325	$155.23	$155.25	$155.20
Purchase #3	$118.52	12.306%	$133.1051	$133.11	$133.10	$133.10
Purchase #4	$74.45	8.308%	$80.6353	$80.64	$80.65	$80.60
Purchase #5	$114.81	11.341%	$127.8306	$127.83	$127.85	$127.80
Purchase #6	$182.83	9.271%	$199.7802	$199.78	$199.80	$199.80
Purchase #7	$155.34	4.489%	$162.3132	$162.31	$162.30	$162.30
7 purchase totals =	$941.03		$1,024.3330	$1,024.34	$1,024.40	$1,024.20