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	$174.91	5.796%	$185.0478	$185.05	$185.05	$185.00
Purchase #2	$80.93	11.292%	$90.0686	$90.07	$90.05	$90.10
Purchase #3	$34.40	9.455%	$37.6525	$37.65	$37.65	$37.70
Purchase #4	$202.43	7.154%	$216.9118	$216.91	$216.90	$216.90
Purchase #5	$58.73	3.709%	$60.9083	$60.91	$60.90	$60.90
Purchase #6	$99.69	3.682%	$103.3606	$103.36	$103.35	$103.40
Purchase #7	$59.39	11.608%	$66.284	$66.28	$66.30	$66.30
7 purchase totals =	$710.48		$760.2336	$760.23	$760.20	$760.30