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	$93.56	11.687%	$104.4944	$104.49	$104.50	$104.50
Purchase #2	$29.61	11.365%	$32.9752	$32.98	$33.00	$33.00
Purchase #3	$133.88	4.373%	$139.7346	$139.73	$139.75	$139.70
Purchase #4	$110.76	6.627%	$118.1001	$118.10	$118.10	$118.10
Purchase #5	$99.44	11.179%	$110.5564	$110.56	$110.55	$110.60
Purchase #6	$10.47	7.564%	$11.262	$11.26	$11.25	$11.30
Purchase #7	$216.34	13.363%	$245.2495	$245.25	$245.25	$245.20
7 purchase totals =	$694.06		$762.3722	$762.37	$762.40	$762.40