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	$247.48	13.830%	$281.7065	$281.71	$281.70	$281.70
Purchase #2	$233.43	13.282%	$264.4342	$264.43	$264.45	$264.40
Purchase #3	$43.83	6.840%	$46.828	$46.83	$46.85	$46.80
Purchase #4	$102.87	5.332%	$108.355	$108.36	$108.35	$108.40
Purchase #5	$105.77	12.674%	$119.1753	$119.18	$119.20	$119.20
Purchase #6	$174.94	4.403%	$182.6426	$182.64	$182.65	$182.60
Purchase #7	$52.64	10.608%	$58.2241	$58.22	$58.20	$58.20
7 purchase totals =	$960.96		$1,061.3657	$1,061.37	$1,061.40	$1,061.30