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	$115.26	4.838%	$120.8363	$120.84	$120.85	$120.80
Purchase #2	$52.75	13.461%	$59.8507	$59.85	$59.85	$59.90
Purchase #3	$233.69	5.515%	$246.578	$246.58	$246.60	$246.60
Purchase #4	$162.63	11.763%	$181.7602	$181.76	$181.75	$181.80
Purchase #5	$29.73	9.668%	$32.6043	$32.60	$32.60	$32.60
Purchase #6	$49.85	11.435%	$55.5503	$55.55	$55.55	$55.60
Purchase #7	$180.33	3.872%	$187.3124	$187.31	$187.30	$187.30
7 purchase totals =	$824.24		$884.4922	$884.49	$884.50	$884.60