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	$181.59	8.150%	$196.3896	$196.39	$196.40	$196.40
Purchase #2	$78.50	6.424%	$83.5428	$83.54	$83.55	$83.50
Purchase #3	$170.98	7.333%	$183.518	$183.52	$183.50	$183.50
Purchase #4	$155.31	8.245%	$168.1153	$168.12	$168.10	$168.10
Purchase #5	$25.58	9.836%	$28.096	$28.10	$28.10	$28.10
Purchase #6	$49.44	13.848%	$56.2865	$56.29	$56.30	$56.30
Purchase #7	$37.97	6.643%	$40.4923	$40.49	$40.50	$40.50
7 purchase totals =	$699.37		$756.4405	$756.45	$756.45	$756.40