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	$164.29	11.114%	$182.5492	$182.55	$182.55	$182.50
Purchase #2	$25.71	6.531%	$27.3891	$27.39	$27.40	$27.40
Purchase #3	$86.43	7.286%	$92.7273	$92.73	$92.75	$92.70
Purchase #4	$28.41	7.222%	$30.4618	$30.46	$30.45	$30.50
Purchase #5	$71.57	12.612%	$80.5964	$80.60	$80.60	$80.60
Purchase #6	$71.37	12.478%	$80.2755	$80.28	$80.30	$80.30
Purchase #7	$100.70	3.747%	$104.4732	$104.47	$104.45	$104.50
7 purchase totals =	$548.48		$598.4725	$598.48	$598.50	$598.50