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	$104.75	12.703%	$118.0564	$118.06	$118.05	$118.10
Purchase #2	$185.25	13.836%	$210.8812	$210.88	$210.90	$210.90
Purchase #3	$28.98	8.747%	$31.5149	$31.51	$31.50	$31.50
Purchase #4	$221.85	6.503%	$236.2769	$236.28	$236.30	$236.30
Purchase #5	$53.90	8.800%	$58.6432	$58.64	$58.65	$58.60
Purchase #6	$164.52	12.647%	$185.3268	$185.33	$185.35	$185.30
Purchase #7	$31.30	8.264%	$33.8866	$33.89	$33.90	$33.90
7 purchase totals =	$790.55		$874.5860	$874.59	$874.65	$874.60