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	$32.48	3.769%	$33.7042	$33.70	$33.70	$33.70
Purchase #2	$140.45	7.279%	$150.6734	$150.67	$150.65	$150.70
Purchase #3	$165.58	6.762%	$176.7765	$176.78	$176.80	$176.80
Purchase #4	$152.42	6.508%	$162.3395	$162.34	$162.35	$162.30
Purchase #5	$88.56	3.762%	$91.8916	$91.89	$91.90	$91.90
Purchase #6	$232.81	4.336%	$242.9046	$242.90	$242.90	$242.90
Purchase #7	$59.96	12.408%	$67.3998	$67.40	$67.40	$67.40
7 purchase totals =	$872.26		$925.6896	$925.68	$925.70	$925.70