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	$79.79	11.733%	$89.1518	$89.15	$89.15	$89.20
Purchase #2	$229.95	13.697%	$261.4463	$261.45	$261.45	$261.40
Purchase #3	$233.29	6.556%	$248.5845	$248.58	$248.60	$248.60
Purchase #4	$169.63	5.763%	$179.4058	$179.41	$179.40	$179.40
Purchase #5	$86.48	7.303%	$92.7956	$92.80	$92.80	$92.80
Purchase #6	$51.79	11.183%	$57.5817	$57.58	$57.60	$57.60
Purchase #7	$209.32	3.147%	$215.9073	$215.91	$215.90	$215.90
7 purchase totals =	$1,060.25		$1,144.8730	$1,144.88	$1,144.90	$1,144.90