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	$101.41	3.617%	$105.078	$105.08	$105.10	$105.10
Purchase #2	$109.33	4.138%	$113.8541	$113.85	$113.85	$113.90
Purchase #3	$43.88	11.513%	$48.9319	$48.93	$48.95	$48.90
Purchase #4	$91.88	12.264%	$103.1482	$103.15	$103.15	$103.10
Purchase #5	$240.34	3.502%	$248.7567	$248.76	$248.75	$248.80
Purchase #6	$90.28	5.354%	$95.1136	$95.11	$95.10	$95.10
Purchase #7	$136.78	3.119%	$141.0462	$141.05	$141.05	$141.00
7 purchase totals =	$813.90		$855.9287	$855.93	$855.95	$855.90