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	$140.42	11.774%	$156.9531	$156.95	$156.95	$157.00
Purchase #2	$169.61	12.806%	$191.3303	$191.33	$191.35	$191.30
Purchase #3	$184.88	5.364%	$194.797	$194.80	$194.80	$194.80
Purchase #4	$214.43	13.669%	$243.7404	$243.74	$243.75	$243.70
Purchase #5	$205.78	5.398%	$216.888	$216.89	$216.90	$216.90
Purchase #6	$51.61	4.162%	$53.758	$53.76	$53.75	$53.80
Purchase #7	$30.81	11.627%	$34.3923	$34.39	$34.40	$34.40
7 purchase totals =	$997.54		$1,091.8591	$1,091.86	$1,091.90	$1,091.90