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	$143.33	7.369%	$153.892	$153.89	$153.90	$153.90
Purchase #2	$146.44	4.291%	$152.7237	$152.72	$152.70	$152.70
Purchase #3	$199.30	8.251%	$215.7442	$215.74	$215.75	$215.70
Purchase #4	$33.77	7.338%	$36.248	$36.25	$36.25	$36.20
Purchase #5	$9.56	5.865%	$10.1207	$10.12	$10.10	$10.10
Purchase #6	$50.98	7.629%	$54.8693	$54.87	$54.85	$54.90
Purchase #7	$156.94	9.492%	$171.8367	$171.84	$171.85	$171.80
7 purchase totals =	$740.32		$795.4346	$795.43	$795.40	$795.30