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	$136.27	10.411%	$150.4571	$150.46	$150.45	$150.50
Purchase #2	$206.46	3.406%	$213.492	$213.49	$213.50	$213.50
Purchase #3	$218.95	13.514%	$248.5389	$248.54	$248.55	$248.50
Purchase #4	$80.39	11.319%	$89.4893	$89.49	$89.50	$89.50
Purchase #5	$131.52	12.308%	$147.7075	$147.71	$147.70	$147.70
Purchase #6	$161.64	10.839%	$179.1602	$179.16	$179.15	$179.20
Purchase #7	$168.93	12.469%	$189.9939	$189.99	$190.00	$190.00
7 purchase totals =	$1,104.16		$1,218.8389	$1,218.84	$1,218.85	$1,218.90