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	$93.81	8.191%	$101.494	$101.49	$101.50	$101.50
Purchase #2	$129.41	5.346%	$136.3283	$136.33	$136.35	$136.30
Purchase #3	$41.73	9.185%	$45.5629	$45.56	$45.55	$45.60
Purchase #4	$203.75	6.476%	$216.9449	$216.94	$216.95	$216.90
Purchase #5	$128.75	10.659%	$142.4735	$142.47	$142.45	$142.50
Purchase #6	$204.25	3.560%	$211.5213	$211.52	$211.50	$211.50
Purchase #7	$169.96	11.492%	$189.4918	$189.49	$189.50	$189.50
7 purchase totals =	$971.66		$1,043.8167	$1,043.80	$1,043.80	$1,043.80