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	$65.89	5.538%	$69.539	$69.54	$69.55	$69.50
Purchase #2	$205.96	12.358%	$231.4125	$231.41	$231.40	$231.40
Purchase #3	$58.43	12.209%	$65.5637	$65.56	$65.55	$65.60
Purchase #4	$205.85	11.666%	$229.8645	$229.86	$229.85	$229.90
Purchase #5	$184.25	8.168%	$199.2995	$199.30	$199.30	$199.30
Purchase #6	$190.26	13.325%	$215.6121	$215.61	$215.60	$215.60
Purchase #7	$35.76	11.418%	$39.8431	$39.84	$39.85	$39.80
7 purchase totals =	$946.40		$1,051.1344	$1,051.12	$1,051.10	$1,051.10