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	$146.71	12.649%	$165.2673	$165.27	$165.25	$165.30
Purchase #2	$194.64	12.532%	$219.0323	$219.03	$219.05	$219.00
Purchase #3	$89.93	12.121%	$100.8304	$100.83	$100.85	$100.80
Purchase #4	$161.62	8.855%	$175.9315	$175.93	$175.95	$175.90
Purchase #5	$158.46	6.218%	$168.313	$168.31	$168.30	$168.30
Purchase #6	$217.39	11.821%	$243.0877	$243.09	$243.10	$243.10
Purchase #7	$63.57	9.597%	$69.6708	$69.67	$69.65	$69.70
7 purchase totals =	$1,032.32		$1,142.1330	$1,142.13	$1,142.15	$1,142.10