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	$47.86	12.327%	$53.7597	$53.76	$53.75	$53.80
Purchase #2	$211.36	10.352%	$233.24	$233.24	$233.25	$233.20
Purchase #3	$118.71	7.660%	$127.8032	$127.80	$127.80	$127.80
Purchase #4	$134.60	5.637%	$142.1874	$142.19	$142.20	$142.20
Purchase #5	$26.39	10.269%	$29.1	$29.10	$29.10	$29.10
Purchase #6	$55.35	3.651%	$57.3708	$57.37	$57.35	$57.40
Purchase #7	$99.57	5.344%	$104.891	$104.89	$104.90	$104.90
7 purchase totals =	$693.84		$748.3521	$748.35	$748.35	$748.40