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	$214.27	6.517%	$228.234	$228.23	$228.25	$228.20
Purchase #2	$219.38	9.445%	$240.1004	$240.10	$240.10	$240.10
Purchase #3	$32.57	7.857%	$35.129	$35.13	$35.15	$35.10
Purchase #4	$175.94	13.870%	$200.3429	$200.34	$200.35	$200.30
Purchase #5	$228.98	3.269%	$236.4654	$236.47	$236.45	$236.50
Purchase #6	$47.71	12.174%	$53.5182	$53.52	$53.50	$53.50
Purchase #7	$144.85	11.868%	$162.0408	$162.04	$162.05	$162.00
7 purchase totals =	$1,063.70		$1,155.8307	$1,155.83	$1,155.85	$1,155.70