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	$174.95	8.464%	$189.7578	$189.76	$189.75	$189.80
Purchase #2	$177.45	13.110%	$200.7137	$200.71	$200.70	$200.70
Purchase #3	$232.53	11.552%	$259.3919	$259.39	$259.40	$259.40
Purchase #4	$131.64	5.751%	$139.2106	$139.21	$139.20	$139.20
Purchase #5	$168.67	8.243%	$182.5735	$182.57	$182.55	$182.60
Purchase #6	$26.91	11.285%	$29.9468	$29.95	$29.95	$29.90
Purchase #7	$142.51	6.183%	$151.3214	$151.32	$151.30	$151.30
7 purchase totals =	$1,054.66		$1,152.9157	$1,152.91	$1,152.85	$1,152.90