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	$57.56	3.867%	$59.7858	$59.79	$59.80	$59.80
Purchase #2	$176.45	12.656%	$198.7815	$198.78	$198.80	$198.80
Purchase #3	$230.91	4.421%	$241.1185	$241.12	$241.10	$241.10
Purchase #4	$26.88	4.650%	$28.1299	$28.13	$28.15	$28.10
Purchase #5	$116.65	13.283%	$132.1446	$132.14	$132.15	$132.10
Purchase #6	$170.67	3.292%	$176.2885	$176.29	$176.30	$176.30
Purchase #7	$243.76	10.300%	$268.8673	$268.87	$268.85	$268.90
7 purchase totals =	$1,022.88		$1,105.1161	$1,105.12	$1,105.15	$1,105.10