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	$55.25	10.428%	$61.0115	$61.01	$61.00	$61.00
Purchase #2	$162.60	10.458%	$179.6047	$179.60	$179.60	$179.60
Purchase #3	$80.78	9.464%	$88.425	$88.43	$88.45	$88.40
Purchase #4	$124.40	7.633%	$133.8955	$133.90	$133.90	$133.90
Purchase #5	$159.35	6.855%	$170.2734	$170.27	$170.25	$170.30
Purchase #6	$233.87	10.346%	$258.0662	$258.07	$258.05	$258.10
Purchase #7	$223.50	12.206%	$250.7804	$250.78	$250.80	$250.80
7 purchase totals =	$1,039.75		$1,142.0567	$1,142.06	$1,142.05	$1,142.10