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	$156.88	5.761%	$165.9179	$165.92	$165.90	$165.90
Purchase #2	$96.99	12.701%	$109.3087	$109.31	$109.30	$109.30
Purchase #3	$217.71	10.304%	$240.1428	$240.14	$240.15	$240.10
Purchase #4	$185.58	13.708%	$211.0193	$211.02	$211.00	$211.00
Purchase #5	$111.26	4.418%	$116.1755	$116.18	$116.20	$116.20
Purchase #6	$52.58	4.330%	$54.8567	$54.86	$54.85	$54.90
Purchase #7	$140.51	9.664%	$154.0889	$154.09	$154.10	$154.10
7 purchase totals =	$961.51		$1,051.5098	$1,051.52	$1,051.50	$1,051.50