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	$207.85	11.159%	$231.044	$231.04	$231.05	$231.00
Purchase #2	$99.72	5.866%	$105.5696	$105.57	$105.55	$105.60
Purchase #3	$195.86	9.342%	$214.1572	$214.16	$214.15	$214.20
Purchase #4	$174.96	12.288%	$196.4591	$196.46	$196.45	$196.50
Purchase #5	$45.32	9.146%	$49.465	$49.47	$49.45	$49.50
Purchase #6	$79.86	6.148%	$84.7698	$84.77	$84.75	$84.80
Purchase #7	$144.63	10.560%	$159.9029	$159.90	$159.90	$159.90
7 purchase totals =	$948.20		$1,041.3676	$1,041.37	$1,041.30	$1,041.50