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	$166.97	7.300%	$179.1588	$179.16	$179.15	$179.20
Purchase #2	$66.69	6.459%	$70.9975	$71.00	$71.00	$71.00
Purchase #3	$124.85	6.307%	$132.7243	$132.72	$132.70	$132.70
Purchase #4	$142.52	3.620%	$147.6792	$147.68	$147.70	$147.70
Purchase #5	$82.61	9.274%	$90.2713	$90.27	$90.25	$90.30
Purchase #6	$150.88	13.345%	$171.0149	$171.01	$171.00	$171.00
Purchase #7	$66.83	6.235%	$70.9969	$71.00	$71.00	$71.00
7 purchase totals =	$801.35		$862.8429	$862.84	$862.80	$862.90