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	$149.91	10.777%	$166.0658	$166.07	$166.05	$166.10
Purchase #2	$199.55	6.863%	$213.2451	$213.25	$213.25	$213.20
Purchase #3	$104.47	13.638%	$118.7176	$118.72	$118.70	$118.70
Purchase #4	$134.38	9.682%	$147.3907	$147.39	$147.40	$147.40
Purchase #5	$188.42	6.563%	$200.786	$200.79	$200.80	$200.80
Purchase #6	$26.92	3.495%	$27.8609	$27.86	$27.85	$27.90
Purchase #7	$196.86	6.840%	$210.3252	$210.33	$210.35	$210.30
7 purchase totals =	$1,000.51		$1,084.3913	$1,084.41	$1,084.40	$1,084.40