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	$116.25	11.234%	$129.3095	$129.31	$129.30	$129.30
Purchase #2	$198.49	10.510%	$219.3513	$219.35	$219.35	$219.40
Purchase #3	$219.38	13.368%	$248.7067	$248.71	$248.70	$248.70
Purchase #4	$93.62	6.695%	$99.8879	$99.89	$99.90	$99.90
Purchase #5	$84.29	12.657%	$94.9586	$94.96	$94.95	$95.00
Purchase #6	$96.93	12.601%	$109.1441	$109.14	$109.15	$109.10
Purchase #7	$192.28	9.110%	$209.7967	$209.80	$209.80	$209.80
7 purchase totals =	$1,001.24		$1,111.1548	$1,111.16	$1,111.15	$1,111.20