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	$78.28	8.661%	$85.0598	$85.06	$85.05	$85.10
Purchase #2	$110.97	6.700%	$118.405	$118.41	$118.40	$118.40
Purchase #3	$31.75	6.785%	$33.9042	$33.90	$33.90	$33.90
Purchase #4	$58.26	5.405%	$61.409	$61.41	$61.40	$61.40
Purchase #5	$18.62	3.477%	$19.2674	$19.27	$19.25	$19.30
Purchase #6	$137.75	11.663%	$153.8158	$153.82	$153.80	$153.80
Purchase #7	$163.33	6.692%	$174.26	$174.26	$174.25	$174.30
7 purchase totals =	$598.96		$646.1212	$646.13	$646.05	$646.20