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	$225.67	7.404%	$242.3786	$242.38	$242.40	$242.40
Purchase #2	$165.56	8.439%	$179.5316	$179.53	$179.55	$179.50
Purchase #3	$218.32	7.304%	$234.2661	$234.27	$234.25	$234.30
Purchase #4	$179.30	6.613%	$191.1571	$191.16	$191.15	$191.20
Purchase #5	$172.39	12.797%	$194.4507	$194.45	$194.45	$194.50
Purchase #6	$163.81	3.159%	$168.9848	$168.98	$169.00	$169.00
Purchase #7	$11.66	13.426%	$13.2255	$13.23	$13.25	$13.20
7 purchase totals =	$1,136.71		$1,223.9944	$1,224.00	$1,224.05	$1,224.10