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	$180.85	10.654%	$200.1178	$200.12	$200.10	$200.10
Purchase #2	$97.92	7.704%	$105.4638	$105.46	$105.45	$105.50
Purchase #3	$166.51	8.246%	$180.2404	$180.24	$180.25	$180.20
Purchase #4	$157.93	9.833%	$173.4593	$173.46	$173.45	$173.50
Purchase #5	$151.32	5.499%	$159.6411	$159.64	$159.65	$159.60
Purchase #6	$81.82	12.648%	$92.1686	$92.17	$92.15	$92.20
Purchase #7	$81.76	12.155%	$91.6979	$91.70	$91.70	$91.70
7 purchase totals =	$918.11		$1,002.7889	$1,002.79	$1,002.75	$1,002.80