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	$186.90	5.112%	$196.4543	$196.45	$196.45	$196.50
Purchase #2	$31.43	13.798%	$35.7667	$35.77	$35.75	$35.80
Purchase #3	$192.88	12.322%	$216.6467	$216.65	$216.65	$216.60
Purchase #4	$188.42	5.721%	$199.1995	$199.20	$199.20	$199.20
Purchase #5	$194.47	11.494%	$216.8224	$216.82	$216.80	$216.80
Purchase #6	$71.88	7.458%	$77.2408	$77.24	$77.25	$77.20
Purchase #7	$146.64	5.269%	$154.3665	$154.37	$154.35	$154.40
7 purchase totals =	$1,012.62		$1,096.4969	$1,096.50	$1,096.45	$1,096.50