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	$101.73	12.112%	$114.0515	$114.05	$114.05	$114.10
Purchase #2	$82.87	4.799%	$86.8469	$86.85	$86.85	$86.80
Purchase #3	$124.75	8.751%	$135.6669	$135.67	$135.65	$135.70
Purchase #4	$99.67	11.722%	$111.3533	$111.35	$111.35	$111.40
Purchase #5	$199.47	5.727%	$210.8936	$210.89	$210.90	$210.90
Purchase #6	$212.78	7.170%	$228.0363	$228.04	$228.05	$228.00
Purchase #7	$89.62	11.714%	$100.1181	$100.12	$100.10	$100.10
7 purchase totals =	$910.89		$986.9666	$986.97	$986.95	$987.00