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	$101.61	11.284%	$113.0757	$113.08	$113.10	$113.10
Purchase #2	$19.52	13.243%	$22.105	$22.11	$22.10	$22.10
Purchase #3	$93.31	5.485%	$98.4281	$98.43	$98.45	$98.40
Purchase #4	$13.58	6.190%	$14.4206	$14.42	$14.40	$14.40
Purchase #5	$18.55	6.638%	$19.7813	$19.78	$19.80	$19.80
Purchase #6	$159.40	12.486%	$179.3027	$179.30	$179.30	$179.30
Purchase #7	$204.44	7.566%	$219.9079	$219.91	$219.90	$219.90
7 purchase totals =	$610.41		$667.0213	$667.03	$667.05	$667.00