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	$91.89	7.607%	$98.8801	$98.88	$98.90	$98.90
Purchase #2	$144.58	3.548%	$149.7097	$149.71	$149.70	$149.70
Purchase #3	$21.80	11.454%	$24.297	$24.30	$24.30	$24.30
Purchase #4	$67.61	12.826%	$76.2817	$76.28	$76.30	$76.30
Purchase #5	$56.70	5.504%	$59.8208	$59.82	$59.80	$59.80
Purchase #6	$7.67	9.818%	$8.423	$8.42	$8.40	$8.40
Purchase #7	$39.48	6.398%	$42.0059	$42.01	$42.00	$42.00
7 purchase totals =	$429.73		$459.4182	$459.42	$459.40	$459.40