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	$152.84	6.295%	$162.4613	$162.46	$162.45	$162.50
Purchase #2	$84.50	13.445%	$95.861	$95.86	$95.85	$95.90
Purchase #3	$226.76	6.206%	$240.8327	$240.83	$240.85	$240.80
Purchase #4	$123.87	13.586%	$140.699	$140.70	$140.70	$140.70
Purchase #5	$72.92	8.437%	$79.0723	$79.07	$79.05	$79.10
Purchase #6	$29.51	11.470%	$32.8948	$32.89	$32.90	$32.90
Purchase #7	$34.80	7.702%	$37.4803	$37.48	$37.50	$37.50
7 purchase totals =	$725.20		$789.3014	$789.29	$789.30	$789.40