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	$92.48	3.146%	$95.3894	$95.39	$95.40	$95.40
Purchase #2	$57.66	4.234%	$60.1013	$60.10	$60.10	$60.10
Purchase #3	$239.95	9.810%	$263.4891	$263.49	$263.50	$263.50
Purchase #4	$43.88	10.391%	$48.4396	$48.44	$48.45	$48.40
Purchase #5	$227.73	6.853%	$243.3363	$243.34	$243.35	$243.30
Purchase #6	$39.35	8.776%	$42.8034	$42.80	$42.80	$42.80
Purchase #7	$237.90	4.565%	$248.7601	$248.76	$248.75	$248.80
7 purchase totals =	$938.95		$1,002.3192	$1,002.32	$1,002.35	$1,002.30