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	$74.69	4.853%	$78.3147	$78.31	$78.30	$78.30
Purchase #2	$119.29	4.115%	$124.1988	$124.20	$124.20	$124.20
Purchase #3	$216.44	10.149%	$238.4065	$238.41	$238.40	$238.40
Purchase #4	$16.78	4.553%	$17.544	$17.54	$17.55	$17.50
Purchase #5	$119.76	6.468%	$127.5061	$127.51	$127.50	$127.50
Purchase #6	$110.26	5.809%	$116.665	$116.67	$116.65	$116.70
Purchase #7	$98.86	4.736%	$103.542	$103.54	$103.55	$103.50
7 purchase totals =	$756.08		$806.1771	$806.18	$806.15	$806.10