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	$98.85	7.654%	$106.416	$106.42	$106.40	$106.40
Purchase #2	$99.29	3.330%	$102.5964	$102.60	$102.60	$102.60
Purchase #3	$134.81	7.435%	$144.8331	$144.83	$144.85	$144.80
Purchase #4	$152.92	3.594%	$158.4159	$158.42	$158.40	$158.40
Purchase #5	$108.73	11.141%	$120.8436	$120.84	$120.85	$120.80
Purchase #6	$207.48	7.448%	$222.9331	$222.93	$222.95	$222.90
Purchase #7	$147.30	13.111%	$166.6125	$166.61	$166.60	$166.60
7 purchase totals =	$949.38		$1,022.6506	$1,022.65	$1,022.65	$1,022.50