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	$122.88	4.826%	$128.8102	$128.81	$128.80	$128.80
Purchase #2	$231.76	5.540%	$244.5995	$244.60	$244.60	$244.60
Purchase #3	$46.72	10.689%	$51.7139	$51.71	$51.70	$51.70
Purchase #4	$53.41	8.328%	$57.858	$57.86	$57.85	$57.90
Purchase #5	$91.63	5.581%	$96.7439	$96.74	$96.75	$96.70
Purchase #6	$38.89	4.273%	$40.5518	$40.55	$40.55	$40.60
Purchase #7	$117.44	11.752%	$131.2415	$131.24	$131.25	$131.20
7 purchase totals =	$702.73		$751.5188	$751.51	$751.50	$751.50