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	$78.50	4.560%	$82.0796	$82.08	$82.10	$82.10
Purchase #2	$185.86	7.661%	$200.0987	$200.10	$200.10	$200.10
Purchase #3	$241.35	6.854%	$257.8921	$257.89	$257.90	$257.90
Purchase #4	$204.90	3.350%	$211.7642	$211.76	$211.75	$211.80
Purchase #5	$21.87	11.504%	$24.3859	$24.39	$24.40	$24.40
Purchase #6	$109.51	4.370%	$114.2956	$114.30	$114.30	$114.30
Purchase #7	$179.77	7.215%	$192.7404	$192.74	$192.75	$192.70
7 purchase totals =	$1,021.76		$1,083.2565	$1,083.26	$1,083.30	$1,083.30