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	$57.37	9.318%	$62.7157	$62.72	$62.70	$62.70
Purchase #2	$234.67	5.810%	$248.3043	$248.30	$248.30	$248.30
Purchase #3	$46.40	12.318%	$52.1156	$52.12	$52.10	$52.10
Purchase #4	$239.85	12.256%	$269.246	$269.25	$269.25	$269.20
Purchase #5	$162.31	11.350%	$180.7322	$180.73	$180.75	$180.70
Purchase #6	$123.52	6.239%	$131.2264	$131.23	$131.25	$131.20
Purchase #7	$74.45	5.358%	$78.439	$78.44	$78.45	$78.40
7 purchase totals =	$938.57		$1,022.7792	$1,022.79	$1,022.80	$1,022.60