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	$49.36	9.837%	$54.2155	$54.22	$54.20	$54.20
Purchase #2	$233.27	10.627%	$258.0596	$258.06	$258.05	$258.10
Purchase #3	$148.32	7.563%	$159.5374	$159.54	$159.55	$159.50
Purchase #4	$60.43	9.668%	$66.2724	$66.27	$66.25	$66.30
Purchase #5	$19.87	11.299%	$22.1151	$22.12	$22.10	$22.10
Purchase #6	$157.64	7.146%	$168.905	$168.91	$168.90	$168.90
Purchase #7	$29.80	13.631%	$33.862	$33.86	$33.85	$33.90
7 purchase totals =	$698.69		$762.9670	$762.98	$762.90	$763.00