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	$160.56	3.147%	$165.6128	$165.61	$165.60	$165.60
Purchase #2	$215.32	9.361%	$235.4761	$235.48	$235.50	$235.50
Purchase #3	$85.83	5.519%	$90.567	$90.57	$90.55	$90.60
Purchase #4	$62.97	4.460%	$65.7785	$65.78	$65.80	$65.80
Purchase #5	$65.58	6.607%	$69.9129	$69.91	$69.90	$69.90
Purchase #6	$227.92	8.715%	$247.7832	$247.78	$247.80	$247.80
Purchase #7	$165.73	6.335%	$176.229	$176.23	$176.25	$176.20
7 purchase totals =	$983.91		$1,051.3595	$1,051.36	$1,051.40	$1,051.40