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	$183.66	6.803%	$196.1544	$196.15	$196.15	$196.20
Purchase #2	$74.63	4.535%	$78.0145	$78.01	$78.00	$78.00
Purchase #3	$154.74	7.480%	$166.3146	$166.31	$166.30	$166.30
Purchase #4	$179.61	6.120%	$190.6021	$190.60	$190.60	$190.60
Purchase #5	$189.69	5.825%	$200.7394	$200.74	$200.75	$200.70
Purchase #6	$245.75	5.384%	$258.9812	$258.98	$259.00	$259.00
Purchase #7	$83.56	7.787%	$90.0668	$90.07	$90.05	$90.10
7 purchase totals =	$1,111.64		$1,180.8730	$1,180.86	$1,180.85	$1,180.90