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	$87.79	7.106%	$94.0284	$94.03	$94.05	$94.00
Purchase #2	$115.36	10.128%	$127.0437	$127.04	$127.05	$127.00
Purchase #3	$54.94	11.193%	$61.0894	$61.09	$61.10	$61.10
Purchase #4	$249.79	4.408%	$260.8007	$260.80	$260.80	$260.80
Purchase #5	$72.66	13.546%	$82.5025	$82.50	$82.50	$82.50
Purchase #6	$72.85	10.356%	$80.3943	$80.39	$80.40	$80.40
Purchase #7	$98.40	3.537%	$101.8804	$101.88	$101.90	$101.90
7 purchase totals =	$751.79		$807.7394	$807.73	$807.80	$807.70