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	$154.53	6.578%	$164.695	$164.70	$164.70	$164.70
Purchase #2	$80.27	6.755%	$85.6922	$85.69	$85.70	$85.70
Purchase #3	$70.80	11.242%	$78.7593	$78.76	$78.75	$78.80
Purchase #4	$10.88	13.260%	$12.3227	$12.32	$12.30	$12.30
Purchase #5	$196.67	4.129%	$204.7905	$204.79	$204.80	$204.80
Purchase #6	$187.79	4.719%	$196.6518	$196.65	$196.65	$196.70
Purchase #7	$225.71	11.431%	$251.5109	$251.51	$251.50	$251.50
7 purchase totals =	$926.65		$994.4224	$994.42	$994.40	$994.50