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	$98.51	12.713%	$111.0336	$111.03	$111.05	$111.00
Purchase #2	$106.99	6.578%	$114.0278	$114.03	$114.05	$114.00
Purchase #3	$19.72	6.800%	$21.061	$21.06	$21.05	$21.10
Purchase #4	$107.50	4.137%	$111.9473	$111.95	$111.95	$111.90
Purchase #5	$76.90	13.435%	$87.2315	$87.23	$87.25	$87.20
Purchase #6	$97.89	9.636%	$107.3227	$107.32	$107.30	$107.30
Purchase #7	$229.68	4.570%	$240.1764	$240.18	$240.20	$240.20
7 purchase totals =	$737.19		$792.8003	$792.80	$792.85	$792.70