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	$184.74	11.874%	$206.676	$206.68	$206.70	$206.70
Purchase #2	$209.35	4.318%	$218.3897	$218.39	$218.40	$218.40
Purchase #3	$121.67	4.559%	$127.2169	$127.22	$127.20	$127.20
Purchase #4	$200.59	8.374%	$217.3874	$217.39	$217.40	$217.40
Purchase #5	$85.42	12.742%	$96.3042	$96.30	$96.30	$96.30
Purchase #6	$109.40	12.599%	$123.1833	$123.18	$123.20	$123.20
Purchase #7	$56.25	9.757%	$61.7383	$61.74	$61.75	$61.70
7 purchase totals =	$967.42		$1,050.8958	$1,050.90	$1,050.95	$1,050.90