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	$242.86	4.475%	$253.728	$253.73	$253.75	$253.70
Purchase #2	$49.61	12.429%	$55.776	$55.78	$55.80	$55.80
Purchase #3	$127.61	3.486%	$132.0585	$132.06	$132.05	$132.10
Purchase #4	$223.52	3.827%	$232.0741	$232.07	$232.05	$232.10
Purchase #5	$193.90	9.187%	$211.7136	$211.71	$211.70	$211.70
Purchase #6	$89.48	10.701%	$99.0553	$99.06	$99.05	$99.10
Purchase #7	$169.54	7.711%	$182.6132	$182.61	$182.60	$182.60
7 purchase totals =	$1,096.52		$1,167.0187	$1,167.02	$1,167.00	$1,167.10