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	$34.94	7.687%	$37.6258	$37.63	$37.65	$37.60
Purchase #2	$122.52	5.378%	$129.1091	$129.11	$129.10	$129.10
Purchase #3	$82.35	8.726%	$89.5359	$89.54	$89.55	$89.50
Purchase #4	$94.26	5.790%	$99.7177	$99.72	$99.70	$99.70
Purchase #5	$202.48	11.496%	$225.7571	$225.76	$225.75	$225.80
Purchase #6	$142.31	6.872%	$152.0895	$152.09	$152.10	$152.10
Purchase #7	$144.62	10.526%	$159.8427	$159.84	$159.85	$159.80
7 purchase totals =	$823.48		$893.6778	$893.69	$893.70	$893.60