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	$114.80	9.550%	$125.7634	$125.76	$125.75	$125.80
Purchase #2	$89.92	10.750%	$99.5864	$99.59	$99.60	$99.60
Purchase #3	$139.94	13.607%	$158.9816	$158.98	$159.00	$159.00
Purchase #4	$115.64	13.743%	$131.5324	$131.53	$131.55	$131.50
Purchase #5	$79.39	5.248%	$83.5564	$83.56	$83.55	$83.60
Purchase #6	$37.53	8.537%	$40.7339	$40.73	$40.75	$40.70
Purchase #7	$216.85	12.408%	$243.7567	$243.76	$243.75	$243.80
7 purchase totals =	$794.07		$883.9108	$883.91	$883.95	$884.00