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	$158.28	10.156%	$174.3549	$174.35	$174.35	$174.40
Purchase #2	$174.34	11.754%	$194.8319	$194.83	$194.85	$194.80
Purchase #3	$53.53	3.787%	$55.5572	$55.56	$55.55	$55.60
Purchase #4	$128.80	8.381%	$139.5947	$139.59	$139.60	$139.60
Purchase #5	$140.86	7.102%	$150.8639	$150.86	$150.85	$150.90
Purchase #6	$33.28	12.379%	$37.3997	$37.40	$37.40	$37.40
Purchase #7	$128.46	11.633%	$143.4038	$143.40	$143.40	$143.40
7 purchase totals =	$817.55		$896.0061	$895.99	$896.00	$896.10