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	$34.53	9.316%	$37.7468	$37.75	$37.75	$37.70
Purchase #2	$209.66	5.107%	$220.3673	$220.37	$220.35	$220.40
Purchase #3	$158.32	8.335%	$171.516	$171.52	$171.50	$171.50
Purchase #4	$59.84	13.871%	$68.1404	$68.14	$68.15	$68.10
Purchase #5	$78.94	4.550%	$82.5318	$82.53	$82.55	$82.50
Purchase #6	$95.68	11.129%	$106.3282	$106.33	$106.35	$106.30
Purchase #7	$25.27	11.815%	$28.2557	$28.26	$28.25	$28.30
7 purchase totals =	$662.24		$714.8862	$714.90	$714.90	$714.80