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	$128.47	11.196%	$142.8535	$142.85	$142.85	$142.90
Purchase #2	$85.44	6.850%	$91.2926	$91.29	$91.30	$91.30
Purchase #3	$184.72	3.204%	$190.6384	$190.64	$190.65	$190.60
Purchase #4	$152.82	11.576%	$170.5104	$170.51	$170.50	$170.50
Purchase #5	$173.97	5.414%	$183.3887	$183.39	$183.40	$183.40
Purchase #6	$43.61	5.230%	$45.8908	$45.89	$45.90	$45.90
Purchase #7	$28.46	9.113%	$31.0536	$31.05	$31.05	$31.10
7 purchase totals =	$797.49		$855.6280	$855.62	$855.65	$855.70