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	$131.60	11.823%	$147.1591	$147.16	$147.15	$147.20
Purchase #2	$236.94	12.332%	$266.1594	$266.16	$266.15	$266.20
Purchase #3	$41.95	13.306%	$47.5319	$47.53	$47.55	$47.50
Purchase #4	$62.35	3.780%	$64.7068	$64.71	$64.70	$64.70
Purchase #5	$32.47	3.479%	$33.5996	$33.60	$33.60	$33.60
Purchase #6	$179.28	9.568%	$196.4335	$196.43	$196.45	$196.40
Purchase #7	$25.86	13.445%	$29.3369	$29.34	$29.35	$29.30
7 purchase totals =	$710.45		$784.9272	$784.93	$784.95	$784.90