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	$149.56	5.437%	$157.6916	$157.69	$157.70	$157.70
Purchase #2	$171.46	8.314%	$185.7152	$185.72	$185.70	$185.70
Purchase #3	$247.88	3.190%	$255.7874	$255.79	$255.80	$255.80
Purchase #4	$90.71	13.123%	$102.6139	$102.61	$102.60	$102.60
Purchase #5	$171.77	4.102%	$178.816	$178.82	$178.80	$178.80
Purchase #6	$115.47	3.396%	$119.3914	$119.39	$119.40	$119.40
Purchase #7	$123.66	3.326%	$127.7729	$127.77	$127.75	$127.80
7 purchase totals =	$1,070.51		$1,127.7884	$1,127.79	$1,127.75	$1,127.80