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	$190.34	8.578%	$206.6674	$206.67	$206.65	$206.70
Purchase #2	$81.36	13.826%	$92.6088	$92.61	$92.60	$92.60
Purchase #3	$157.72	3.148%	$162.685	$162.69	$162.70	$162.70
Purchase #4	$77.60	10.227%	$85.5362	$85.54	$85.55	$85.50
Purchase #5	$58.38	5.663%	$61.6861	$61.69	$61.70	$61.70
Purchase #6	$127.59	3.180%	$131.6474	$131.65	$131.65	$131.60
Purchase #7	$181.95	4.320%	$189.8102	$189.81	$189.80	$189.80
7 purchase totals =	$874.94		$930.6411	$930.66	$930.65	$930.60