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	$237.97	13.223%	$269.4368	$269.44	$269.45	$269.40
Purchase #2	$135.85	12.336%	$152.6085	$152.61	$152.60	$152.60
Purchase #3	$45.37	9.673%	$49.7586	$49.76	$49.75	$49.80
Purchase #4	$235.67	12.657%	$265.4988	$265.50	$265.50	$265.50
Purchase #5	$151.55	11.503%	$168.9828	$168.98	$169.00	$169.00
Purchase #6	$47.83	11.444%	$53.3037	$53.30	$53.30	$53.30
Purchase #7	$55.99	11.571%	$62.4686	$62.47	$62.45	$62.50
7 purchase totals =	$910.23		$1,022.0578	$1,022.06	$1,022.05	$1,022.10