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	$33.60	11.128%	$37.339	$37.34	$37.35	$37.30
Purchase #2	$76.26	12.507%	$85.7978	$85.80	$85.80	$85.80
Purchase #3	$46.62	12.146%	$52.2825	$52.28	$52.30	$52.30
Purchase #4	$74.44	5.543%	$78.5662	$78.57	$78.55	$78.60
Purchase #5	$28.68	6.839%	$30.6414	$30.64	$30.65	$30.60
Purchase #6	$82.55	3.668%	$85.5779	$85.58	$85.60	$85.60
Purchase #7	$65.89	11.149%	$73.2361	$73.24	$73.25	$73.20
7 purchase totals =	$408.04		$443.4409	$443.45	$443.50	$443.40