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	$91.40	12.580%	$102.8981	$102.90	$102.90	$102.90
Purchase #2	$199.46	11.278%	$221.9551	$221.96	$221.95	$222.00
Purchase #3	$83.46	10.862%	$92.5254	$92.53	$92.55	$92.50
Purchase #4	$223.96	8.402%	$242.7771	$242.78	$242.80	$242.80
Purchase #5	$58.70	10.267%	$64.7267	$64.73	$64.75	$64.70
Purchase #6	$218.36	11.668%	$243.8382	$243.84	$243.85	$243.80
Purchase #7	$216.36	5.316%	$227.8617	$227.86	$227.85	$227.90
7 purchase totals =	$1,091.70		$1,196.5823	$1,196.60	$1,196.65	$1,196.60