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	$93.84	4.715%	$98.2646	$98.26	$98.25	$98.30
Purchase #2	$32.49	9.183%	$35.4736	$35.47	$35.45	$35.50
Purchase #3	$209.98	6.503%	$223.635	$223.64	$223.65	$223.60
Purchase #4	$161.81	8.163%	$175.0186	$175.02	$175.00	$175.00
Purchase #5	$6.70	6.470%	$7.1335	$7.13	$7.15	$7.10
Purchase #6	$98.76	10.458%	$109.0883	$109.09	$109.10	$109.10
Purchase #7	$145.89	13.535%	$165.6362	$165.64	$165.65	$165.60
7 purchase totals =	$749.47		$814.2498	$814.25	$814.25	$814.20