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	$99.27	6.736%	$105.9568	$105.96	$105.95	$106.00
Purchase #2	$224.45	11.390%	$250.0149	$250.01	$250.00	$250.00
Purchase #3	$53.36	4.119%	$55.5579	$55.56	$55.55	$55.60
Purchase #4	$65.62	6.251%	$69.7219	$69.72	$69.70	$69.70
Purchase #5	$183.66	13.828%	$209.0565	$209.06	$209.05	$209.10
Purchase #6	$233.56	11.614%	$260.6857	$260.69	$260.70	$260.70
Purchase #7	$133.60	9.577%	$146.3949	$146.39	$146.40	$146.40
7 purchase totals =	$993.52		$1,097.3886	$1,097.39	$1,097.35	$1,097.50