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	$215.69	12.412%	$242.4614	$242.46	$242.45	$242.50
Purchase #2	$240.40	11.794%	$268.7528	$268.75	$268.75	$268.80
Purchase #3	$191.43	5.435%	$201.8342	$201.83	$201.85	$201.80
Purchase #4	$78.56	6.744%	$83.8581	$83.86	$83.85	$83.90
Purchase #5	$28.62	13.521%	$32.4897	$32.49	$32.50	$32.50
Purchase #6	$50.83	13.315%	$57.598	$57.60	$57.60	$57.60
Purchase #7	$33.72	11.644%	$37.6464	$37.65	$37.65	$37.60
7 purchase totals =	$839.25		$924.6406	$924.64	$924.65	$924.70