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	$140.73	9.353%	$153.8925	$153.89	$153.90	$153.90
Purchase #2	$137.25	11.119%	$152.5108	$152.51	$152.50	$152.50
Purchase #3	$123.88	4.321%	$129.2329	$129.23	$129.25	$129.20
Purchase #4	$55.83	6.120%	$59.2468	$59.25	$59.25	$59.20
Purchase #5	$237.28	11.318%	$264.1354	$264.14	$264.15	$264.10
Purchase #6	$44.81	4.259%	$46.7185	$46.72	$46.70	$46.70
Purchase #7	$118.41	8.819%	$128.8526	$128.85	$128.85	$128.90
7 purchase totals =	$858.19		$934.5895	$934.59	$934.60	$934.50