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	$83.75	3.265%	$86.4844	$86.48	$86.50	$86.50
Purchase #2	$19.95	8.479%	$21.6416	$21.64	$21.65	$21.60
Purchase #3	$104.74	12.594%	$117.931	$117.93	$117.95	$117.90
Purchase #4	$53.92	10.272%	$59.4587	$59.46	$59.45	$59.50
Purchase #5	$165.67	5.665%	$175.0552	$175.06	$175.05	$175.10
Purchase #6	$130.47	3.205%	$134.6516	$134.65	$134.65	$134.70
Purchase #7	$67.94	4.685%	$71.123	$71.12	$71.10	$71.10
7 purchase totals =	$626.44		$666.3455	$666.34	$666.35	$666.40