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	$89.83	4.199%	$93.602	$93.60	$93.60	$93.60
Purchase #2	$142.32	13.870%	$162.0598	$162.06	$162.05	$162.10
Purchase #3	$121.51	7.482%	$130.6014	$130.60	$130.60	$130.60
Purchase #4	$237.87	9.203%	$259.7612	$259.76	$259.75	$259.80
Purchase #5	$127.27	11.162%	$141.4759	$141.48	$141.50	$141.50
Purchase #6	$223.42	12.752%	$251.9105	$251.91	$251.90	$251.90
Purchase #7	$37.64	3.374%	$38.91	$38.91	$38.90	$38.90
7 purchase totals =	$979.86		$1,078.3208	$1,078.32	$1,078.30	$1,078.40