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	$99.45	6.499%	$105.9133	$105.91	$105.90	$105.90
Purchase #2	$165.46	6.106%	$175.563	$175.56	$175.55	$175.60
Purchase #3	$101.91	7.446%	$109.4982	$109.50	$109.50	$109.50
Purchase #4	$212.79	7.525%	$228.8024	$228.80	$228.80	$228.80
Purchase #5	$64.86	11.593%	$72.3792	$72.38	$72.40	$72.40
Purchase #6	$173.90	6.323%	$184.8957	$184.90	$184.90	$184.90
Purchase #7	$108.45	10.392%	$119.7201	$119.72	$119.70	$119.70
7 purchase totals =	$926.82		$996.7719	$996.77	$996.75	$996.80