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	$175.47	4.384%	$183.1626	$183.16	$183.15	$183.20
Purchase #2	$89.71	12.411%	$100.8439	$100.84	$100.85	$100.80
Purchase #3	$162.80	5.143%	$171.1728	$171.17	$171.15	$171.20
Purchase #4	$41.45	4.487%	$43.3099	$43.31	$43.30	$43.30
Purchase #5	$88.53	4.564%	$92.5705	$92.57	$92.55	$92.60
Purchase #6	$188.95	13.213%	$213.916	$213.92	$213.90	$213.90
Purchase #7	$56.92	13.638%	$64.6827	$64.68	$64.70	$64.70
7 purchase totals =	$803.83		$869.6584	$869.65	$869.60	$869.70