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	$210.71	6.277%	$223.9363	$223.94	$223.95	$223.90
Purchase #2	$192.61	13.411%	$218.4409	$218.44	$218.45	$218.40
Purchase #3	$101.42	12.223%	$113.8166	$113.82	$113.80	$113.80
Purchase #4	$231.47	11.524%	$258.1446	$258.14	$258.15	$258.10
Purchase #5	$61.84	8.575%	$67.1428	$67.14	$67.15	$67.10
Purchase #6	$175.59	8.424%	$190.3817	$190.38	$190.40	$190.40
Purchase #7	$84.69	10.425%	$93.5189	$93.52	$93.50	$93.50
7 purchase totals =	$1,058.33		$1,165.3818	$1,165.38	$1,165.40	$1,165.20