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	$189.91	10.111%	$209.1118	$209.11	$209.10	$209.10
Purchase #2	$177.78	10.594%	$196.614	$196.61	$196.60	$196.60
Purchase #3	$82.67	10.181%	$91.0866	$91.09	$91.10	$91.10
Purchase #4	$102.53	6.433%	$109.1258	$109.13	$109.15	$109.10
Purchase #5	$82.50	13.750%	$93.8438	$93.84	$93.85	$93.80
Purchase #6	$44.92	12.540%	$50.553	$50.55	$50.55	$50.60
Purchase #7	$238.43	11.827%	$266.6291	$266.63	$266.65	$266.60
7 purchase totals =	$918.74		$1,016.9641	$1,016.96	$1,017.00	$1,016.90