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	$198.55	6.559%	$211.5729	$211.57	$211.55	$211.60
Purchase #2	$144.25	9.747%	$158.31	$158.31	$158.30	$158.30
Purchase #3	$165.85	5.145%	$174.383	$174.38	$174.40	$174.40
Purchase #4	$248.53	9.204%	$271.4047	$271.40	$271.40	$271.40
Purchase #5	$12.44	12.269%	$13.9663	$13.97	$13.95	$14.00
Purchase #6	$174.34	8.268%	$188.7544	$188.75	$188.75	$188.80
Purchase #7	$92.59	13.663%	$105.2406	$105.24	$105.25	$105.20
7 purchase totals =	$1,036.55		$1,123.6319	$1,123.62	$1,123.60	$1,123.70