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	$63.44	6.756%	$67.726	$67.73	$67.75	$67.70
Purchase #2	$107.35	8.688%	$116.6766	$116.68	$116.70	$116.70
Purchase #3	$159.66	9.154%	$174.2753	$174.28	$174.30	$174.30
Purchase #4	$171.80	10.741%	$190.253	$190.25	$190.25	$190.30
Purchase #5	$160.61	3.637%	$166.4514	$166.45	$166.45	$166.50
Purchase #6	$123.52	3.834%	$128.2558	$128.26	$128.25	$128.30
Purchase #7	$173.69	4.419%	$181.3654	$181.37	$181.35	$181.40
7 purchase totals =	$960.07		$1,025.0035	$1,025.02	$1,025.05	$1,025.20