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	$92.25	11.531%	$102.8873	$102.89	$102.90	$102.90
Purchase #2	$67.66	4.572%	$70.7534	$70.75	$70.75	$70.80
Purchase #3	$111.69	6.125%	$118.531	$118.53	$118.55	$118.50
Purchase #4	$223.73	13.755%	$254.5041	$254.50	$254.50	$254.50
Purchase #5	$28.68	4.240%	$29.896	$29.90	$29.90	$29.90
Purchase #6	$215.40	4.572%	$225.2481	$225.25	$225.25	$225.20
Purchase #7	$89.97	7.716%	$96.9121	$96.91	$96.90	$96.90
7 purchase totals =	$829.38		$898.7320	$898.73	$898.75	$898.70