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	$198.35	5.817%	$209.888	$209.89	$209.90	$209.90
Purchase #2	$58.69	9.563%	$64.3025	$64.30	$64.30	$64.30
Purchase #3	$60.72	10.538%	$67.1187	$67.12	$67.10	$67.10
Purchase #4	$81.78	8.121%	$88.4214	$88.42	$88.40	$88.40
Purchase #5	$153.30	7.822%	$165.2911	$165.29	$165.30	$165.30
Purchase #6	$210.29	8.237%	$227.6116	$227.61	$227.60	$227.60
Purchase #7	$168.35	12.335%	$189.116	$189.12	$189.10	$189.10
7 purchase totals =	$931.48		$1,011.7493	$1,011.75	$1,011.70	$1,011.70