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	$191.40	4.683%	$200.3633	$200.36	$200.35	$200.40
Purchase #2	$250.56	3.300%	$258.8285	$258.83	$258.85	$258.80
Purchase #3	$106.77	7.464%	$114.7393	$114.74	$114.75	$114.70
Purchase #4	$98.81	5.798%	$104.539	$104.54	$104.55	$104.50
Purchase #5	$73.91	12.749%	$83.3328	$83.33	$83.35	$83.30
Purchase #6	$53.87	11.856%	$60.2568	$60.26	$60.25	$60.30
Purchase #7	$194.35	7.730%	$209.3733	$209.37	$209.35	$209.40
7 purchase totals =	$969.67		$1,031.4330	$1,031.43	$1,031.45	$1,031.40