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	$211.32	5.164%	$222.2326	$222.23	$222.25	$222.20
Purchase #2	$29.96	6.622%	$31.944	$31.94	$31.95	$31.90
Purchase #3	$161.56	6.366%	$171.8449	$171.84	$171.85	$171.80
Purchase #4	$40.36	11.251%	$44.9009	$44.90	$44.90	$44.90
Purchase #5	$19.48	13.213%	$22.0539	$22.05	$22.05	$22.10
Purchase #6	$175.83	12.423%	$197.6734	$197.67	$197.65	$197.70
Purchase #7	$101.30	9.764%	$111.1909	$111.19	$111.20	$111.20
7 purchase totals =	$739.81		$801.8406	$801.82	$801.85	$801.80