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	$72.72	8.565%	$78.9485	$78.95	$78.95	$78.90
Purchase #2	$189.99	3.163%	$195.9994	$196.00	$196.00	$196.00
Purchase #3	$108.57	9.414%	$118.7908	$118.79	$118.80	$118.80
Purchase #4	$215.91	6.425%	$229.7822	$229.78	$229.80	$229.80
Purchase #5	$160.95	3.689%	$166.8874	$166.89	$166.90	$166.90
Purchase #6	$164.96	6.433%	$175.5719	$175.57	$175.55	$175.60
Purchase #7	$141.81	10.437%	$156.6107	$156.61	$156.60	$156.60
7 purchase totals =	$1,054.91		$1,122.5909	$1,122.59	$1,122.60	$1,122.60