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	$238.79	10.744%	$264.4456	$264.45	$264.45	$264.40
Purchase #2	$106.78	5.402%	$112.5483	$112.55	$112.55	$112.50
Purchase #3	$208.93	3.727%	$216.7168	$216.72	$216.70	$216.70
Purchase #4	$88.90	11.540%	$99.1591	$99.16	$99.15	$99.20
Purchase #5	$185.46	12.696%	$209.006	$209.01	$209.00	$209.00
Purchase #6	$113.37	12.309%	$127.3247	$127.32	$127.30	$127.30
Purchase #7	$120.81	3.828%	$125.4346	$125.43	$125.45	$125.40
7 purchase totals =	$1,063.04		$1,154.6351	$1,154.64	$1,154.60	$1,154.50