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	$190.28	10.120%	$209.5363	$209.54	$209.55	$209.50
Purchase #2	$143.89	4.382%	$150.1953	$150.20	$150.20	$150.20
Purchase #3	$80.43	6.401%	$85.5783	$85.58	$85.60	$85.60
Purchase #4	$175.96	7.604%	$189.34	$189.34	$189.35	$189.30
Purchase #5	$215.98	12.481%	$242.9365	$242.94	$242.95	$242.90
Purchase #6	$239.84	10.200%	$264.3037	$264.30	$264.30	$264.30
Purchase #7	$73.63	6.552%	$78.4542	$78.45	$78.45	$78.50
7 purchase totals =	$1,120.01		$1,220.3443	$1,220.35	$1,220.40	$1,220.30