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	$74.62	4.165%	$77.7279	$77.73	$77.75	$77.70
Purchase #2	$130.95	13.307%	$148.3755	$148.38	$148.40	$148.40
Purchase #3	$77.48	3.201%	$79.9601	$79.96	$79.95	$80.00
Purchase #4	$227.83	6.719%	$243.1379	$243.14	$243.15	$243.10
Purchase #5	$179.94	4.787%	$188.5537	$188.55	$188.55	$188.60
Purchase #6	$209.32	10.742%	$231.8052	$231.81	$231.80	$231.80
Purchase #7	$172.50	13.855%	$196.3999	$196.40	$196.40	$196.40
7 purchase totals =	$1,072.64		$1,165.9602	$1,165.97	$1,166.00	$1,166.00