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	$139.51	8.255%	$151.0266	$151.03	$151.05	$151.00
Purchase #2	$44.71	5.495%	$47.1668	$47.17	$47.15	$47.20
Purchase #3	$193.54	6.297%	$205.7272	$205.73	$205.75	$205.70
Purchase #4	$112.32	13.752%	$127.7662	$127.77	$127.75	$127.80
Purchase #5	$131.56	6.816%	$140.5271	$140.53	$140.55	$140.50
Purchase #6	$152.65	12.563%	$171.8274	$171.83	$171.85	$171.80
Purchase #7	$79.98	3.319%	$82.6345	$82.63	$82.65	$82.60
7 purchase totals =	$854.27		$926.6758	$926.69	$926.75	$926.60