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	$175.27	9.172%	$191.3458	$191.35	$191.35	$191.30
Purchase #2	$173.84	7.825%	$187.443	$187.44	$187.45	$187.40
Purchase #3	$223.91	4.204%	$233.3232	$233.32	$233.30	$233.30
Purchase #4	$126.70	3.636%	$131.3068	$131.31	$131.30	$131.30
Purchase #5	$182.33	3.824%	$189.3023	$189.30	$189.30	$189.30
Purchase #6	$94.26	10.382%	$104.0461	$104.05	$104.05	$104.00
Purchase #7	$76.97	13.241%	$87.1616	$87.16	$87.15	$87.20
7 purchase totals =	$1,053.28		$1,123.9288	$1,123.93	$1,123.90	$1,123.80