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	$100.41	10.659%	$111.1127	$111.11	$111.10	$111.10
Purchase #2	$60.82	9.514%	$66.6064	$66.61	$66.60	$66.60
Purchase #3	$209.28	4.543%	$218.7876	$218.79	$218.80	$218.80
Purchase #4	$85.80	12.711%	$96.706	$96.71	$96.70	$96.70
Purchase #5	$13.87	3.256%	$14.3216	$14.32	$14.30	$14.30
Purchase #6	$43.32	13.361%	$49.108	$49.11	$49.10	$49.10
Purchase #7	$155.56	10.640%	$172.1116	$172.11	$172.10	$172.10
7 purchase totals =	$669.06		$728.7539	$728.76	$728.70	$728.70