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	$110.35	5.643%	$116.5771	$116.58	$116.60	$116.60
Purchase #2	$219.57	13.361%	$248.9067	$248.91	$248.90	$248.90
Purchase #3	$222.74	11.558%	$248.4843	$248.48	$248.50	$248.50
Purchase #4	$175.54	8.782%	$190.9559	$190.96	$190.95	$191.00
Purchase #5	$44.61	4.240%	$46.5015	$46.50	$46.50	$46.50
Purchase #6	$102.71	6.399%	$109.2824	$109.28	$109.30	$109.30
Purchase #7	$39.46	12.117%	$44.2414	$44.24	$44.25	$44.20
7 purchase totals =	$914.98		$1,004.9493	$1,004.95	$1,005.00	$1,005.00