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	$168.87	9.287%	$184.553	$184.55	$184.55	$184.60
Purchase #2	$74.93	5.208%	$78.8324	$78.83	$78.85	$78.80
Purchase #3	$90.46	11.539%	$100.8982	$100.90	$100.90	$100.90
Purchase #4	$91.98	3.414%	$95.1202	$95.12	$95.10	$95.10
Purchase #5	$110.33	11.712%	$123.2518	$123.25	$123.25	$123.30
Purchase #6	$17.41	12.618%	$19.6068	$19.61	$19.60	$19.60
Purchase #7	$48.45	3.430%	$50.1118	$50.11	$50.10	$50.10
7 purchase totals =	$602.43		$652.3742	$652.37	$652.35	$652.40