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	$174.60	12.689%	$196.755	$196.76	$196.75	$196.80
Purchase #2	$212.58	7.839%	$229.2441	$229.24	$229.25	$229.20
Purchase #3	$168.95	13.523%	$191.7971	$191.80	$191.80	$191.80
Purchase #4	$109.57	5.651%	$115.7618	$115.76	$115.75	$115.80
Purchase #5	$157.96	9.431%	$172.8572	$172.86	$172.85	$172.90
Purchase #6	$107.98	13.817%	$122.8996	$122.90	$122.90	$122.90
Purchase #7	$71.46	9.362%	$78.1501	$78.15	$78.15	$78.20
7 purchase totals =	$1,003.10		$1,107.4649	$1,107.47	$1,107.45	$1,107.60