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	$156.43	4.114%	$162.8655	$162.87	$162.85	$162.90
Purchase #2	$71.43	10.538%	$78.9573	$78.96	$78.95	$79.00
Purchase #3	$45.37	4.400%	$47.3663	$47.37	$47.35	$47.40
Purchase #4	$39.81	6.486%	$42.3921	$42.39	$42.40	$42.40
Purchase #5	$41.42	11.821%	$46.3163	$46.32	$46.30	$46.30
Purchase #6	$12.63	7.571%	$13.5862	$13.59	$13.60	$13.60
Purchase #7	$17.40	7.371%	$18.6826	$18.68	$18.70	$18.70
7 purchase totals =	$384.49		$410.1663	$410.18	$410.15	$410.30