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	$56.54	13.753%	$64.3159	$64.32	$64.30	$64.30
Purchase #2	$131.46	13.570%	$149.2991	$149.30	$149.30	$149.30
Purchase #3	$76.53	5.107%	$80.4384	$80.44	$80.45	$80.40
Purchase #4	$56.25	5.787%	$59.5052	$59.51	$59.50	$59.50
Purchase #5	$200.81	4.468%	$209.7822	$209.78	$209.80	$209.80
Purchase #6	$127.41	9.109%	$139.0158	$139.02	$139.00	$139.00
Purchase #7	$28.40	11.406%	$31.6393	$31.64	$31.65	$31.60
7 purchase totals =	$677.40		$733.9959	$734.01	$734.00	$733.90