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	$92.88	4.304%	$96.8776	$96.88	$96.90	$96.90
Purchase #2	$234.60	13.427%	$266.0997	$266.10	$266.10	$266.10
Purchase #3	$201.67	10.708%	$223.2648	$223.26	$223.25	$223.30
Purchase #4	$72.89	8.453%	$79.0514	$79.05	$79.05	$79.10
Purchase #5	$66.39	6.366%	$70.6164	$70.62	$70.60	$70.60
Purchase #6	$182.75	11.785%	$204.2871	$204.29	$204.30	$204.30
Purchase #7	$74.71	10.372%	$82.4589	$82.46	$82.45	$82.50
7 purchase totals =	$925.89		$1,022.6559	$1,022.66	$1,022.65	$1,022.80