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	$90.41	8.411%	$98.0144	$98.01	$98.00	$98.00
Purchase #2	$231.41	10.297%	$255.2383	$255.24	$255.25	$255.20
Purchase #3	$22.76	11.685%	$25.4195	$25.42	$25.40	$25.40
Purchase #4	$26.61	6.439%	$28.3234	$28.32	$28.30	$28.30
Purchase #5	$89.35	6.193%	$94.8834	$94.88	$94.90	$94.90
Purchase #6	$138.78	5.399%	$146.2727	$146.27	$146.25	$146.30
Purchase #7	$76.81	8.485%	$83.3273	$83.33	$83.35	$83.30
7 purchase totals =	$676.13		$731.4790	$731.47	$731.45	$731.40