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	$219.52	6.321%	$233.3959	$233.40	$233.40	$233.40
Purchase #2	$71.43	9.562%	$78.2601	$78.26	$78.25	$78.30
Purchase #3	$164.53	5.552%	$173.6647	$173.66	$173.65	$173.70
Purchase #4	$96.49	12.677%	$108.722	$108.72	$108.70	$108.70
Purchase #5	$56.83	4.582%	$59.434	$59.43	$59.45	$59.40
Purchase #6	$120.57	3.207%	$124.4367	$124.44	$124.45	$124.40
Purchase #7	$98.53	11.441%	$109.8028	$109.80	$109.80	$109.80
7 purchase totals =	$827.90		$887.7162	$887.71	$887.70	$887.70