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	$88.54	8.107%	$95.7179	$95.72	$95.70	$95.70
Purchase #2	$145.40	13.749%	$165.391	$165.39	$165.40	$165.40
Purchase #3	$129.85	6.516%	$138.311	$138.31	$138.30	$138.30
Purchase #4	$172.76	13.608%	$196.2692	$196.27	$196.25	$196.30
Purchase #5	$98.56	3.506%	$102.0155	$102.02	$102.00	$102.00
Purchase #6	$26.27	5.385%	$27.6846	$27.68	$27.70	$27.70
Purchase #7	$53.31	6.722%	$56.8935	$56.89	$56.90	$56.90
7 purchase totals =	$714.69		$782.2827	$782.28	$782.25	$782.30