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	$60.60	11.304%	$67.4502	$67.45	$67.45	$67.50
Purchase #2	$221.43	11.166%	$246.1549	$246.15	$246.15	$246.20
Purchase #3	$96.89	6.735%	$103.4155	$103.42	$103.40	$103.40
Purchase #4	$212.77	11.731%	$237.73	$237.73	$237.75	$237.70
Purchase #5	$226.91	6.173%	$240.9172	$240.92	$240.90	$240.90
Purchase #6	$209.66	6.651%	$223.6045	$223.60	$223.60	$223.60
Purchase #7	$36.38	5.192%	$38.2688	$38.27	$38.25	$38.30
7 purchase totals =	$1,064.64		$1,157.5411	$1,157.54	$1,157.50	$1,157.60