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	$161.50	7.591%	$173.7595	$173.76	$173.75	$173.80
Purchase #2	$110.52	7.206%	$118.4841	$118.48	$118.50	$118.50
Purchase #3	$243.44	11.456%	$271.3285	$271.33	$271.35	$271.30
Purchase #4	$242.57	4.102%	$252.5202	$252.52	$252.50	$252.50
Purchase #5	$42.76	7.309%	$45.8853	$45.89	$45.90	$45.90
Purchase #6	$28.92	13.527%	$32.832	$32.83	$32.85	$32.80
Purchase #7	$39.75	6.287%	$42.2491	$42.25	$42.25	$42.20
7 purchase totals =	$869.46		$937.0587	$937.06	$937.10	$937.00