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	$169.96	12.537%	$191.2679	$191.27	$191.25	$191.30
Purchase #2	$183.38	9.262%	$200.3647	$200.36	$200.35	$200.40
Purchase #3	$53.45	8.169%	$57.8163	$57.82	$57.80	$57.80
Purchase #4	$106.67	5.715%	$112.7662	$112.77	$112.75	$112.80
Purchase #5	$148.45	6.254%	$157.7341	$157.73	$157.75	$157.70
Purchase #6	$136.86	5.628%	$144.5625	$144.56	$144.55	$144.60
Purchase #7	$194.43	8.435%	$210.8302	$210.83	$210.85	$210.80
7 purchase totals =	$993.20		$1,075.3419	$1,075.34	$1,075.30	$1,075.40