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	$235.92	4.118%	$245.6352	$245.64	$245.65	$245.60
Purchase #2	$16.55	8.705%	$17.9907	$17.99	$18.00	$18.00
Purchase #3	$68.33	5.792%	$72.2877	$72.29	$72.30	$72.30
Purchase #4	$10.46	13.529%	$11.8751	$11.88	$11.90	$11.90
Purchase #5	$82.73	8.717%	$89.9416	$89.94	$89.95	$89.90
Purchase #6	$212.58	13.437%	$241.1444	$241.14	$241.15	$241.10
Purchase #7	$59.79	7.816%	$64.4632	$64.46	$64.45	$64.50
7 purchase totals =	$686.36		$743.3379	$743.34	$743.40	$743.30