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	$24.36	4.134%	$25.367	$25.37	$25.35	$25.40
Purchase #2	$103.56	8.487%	$112.3491	$112.35	$112.35	$112.30
Purchase #3	$147.77	13.178%	$167.2431	$167.24	$167.25	$167.20
Purchase #4	$186.76	12.657%	$210.3982	$210.40	$210.40	$210.40
Purchase #5	$77.41	10.423%	$85.4784	$85.48	$85.50	$85.50
Purchase #6	$200.42	5.528%	$211.4992	$211.50	$211.50	$211.50
Purchase #7	$88.34	3.601%	$91.5211	$91.52	$91.50	$91.50
7 purchase totals =	$828.62		$903.8561	$903.86	$903.85	$903.80