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	$41.25	10.700%	$45.6638	$45.66	$45.65	$45.70
Purchase #2	$245.31	5.533%	$258.883	$258.88	$258.90	$258.90
Purchase #3	$91.96	9.458%	$100.6576	$100.66	$100.65	$100.70
Purchase #4	$133.87	3.545%	$138.6157	$138.62	$138.60	$138.60
Purchase #5	$53.31	13.166%	$60.3288	$60.33	$60.35	$60.30
Purchase #6	$56.80	9.174%	$62.0108	$62.01	$62.00	$62.00
Purchase #7	$246.92	3.621%	$255.861	$255.86	$255.85	$255.90
7 purchase totals =	$869.42		$922.0207	$922.02	$922.00	$922.10