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	$150.30	4.230%	$156.6577	$156.66	$156.65	$156.70
Purchase #2	$43.83	7.591%	$47.1571	$47.16	$47.15	$47.20
Purchase #3	$159.38	5.202%	$167.6709	$167.67	$167.65	$167.70
Purchase #4	$99.95	9.830%	$109.7751	$109.78	$109.80	$109.80
Purchase #5	$203.64	8.788%	$221.5359	$221.54	$221.55	$221.50
Purchase #6	$42.35	12.838%	$47.7869	$47.79	$47.80	$47.80
Purchase #7	$250.41	12.795%	$282.45	$282.45	$282.45	$282.50
7 purchase totals =	$949.86		$1,033.0336	$1,033.05	$1,033.05	$1,033.20