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	$142.82	7.255%	$153.1816	$153.18	$153.20	$153.20
Purchase #2	$49.28	3.189%	$50.8515	$50.85	$50.85	$50.90
Purchase #3	$213.33	3.731%	$221.2893	$221.29	$221.30	$221.30
Purchase #4	$105.85	3.224%	$109.2626	$109.26	$109.25	$109.30
Purchase #5	$55.60	11.331%	$61.9	$61.90	$61.90	$61.90
Purchase #6	$136.40	8.267%	$147.6762	$147.68	$147.70	$147.70
Purchase #7	$82.49	8.357%	$89.3837	$89.38	$89.40	$89.40
7 purchase totals =	$785.77		$833.5449	$833.54	$833.60	$833.70