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	$32.94	12.736%	$37.1352	$37.14	$37.15	$37.10
Purchase #2	$157.90	5.847%	$167.1324	$167.13	$167.15	$167.10
Purchase #3	$100.76	5.314%	$106.1144	$106.11	$106.10	$106.10
Purchase #4	$176.41	3.591%	$182.7449	$182.74	$182.75	$182.70
Purchase #5	$47.82	11.459%	$53.2997	$53.30	$53.30	$53.30
Purchase #6	$78.80	7.591%	$84.7817	$84.78	$84.80	$84.80
Purchase #7	$47.90	13.562%	$54.3962	$54.40	$54.40	$54.40
7 purchase totals =	$642.53		$685.6045	$685.60	$685.65	$685.50