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	$186.34	5.367%	$196.3409	$196.34	$196.35	$196.30
Purchase #2	$227.86	3.236%	$235.2335	$235.23	$235.25	$235.20
Purchase #3	$210.99	8.496%	$228.9157	$228.92	$228.90	$228.90
Purchase #4	$250.44	4.389%	$261.4318	$261.43	$261.45	$261.40
Purchase #5	$27.59	5.575%	$29.1281	$29.13	$29.15	$29.10
Purchase #6	$131.78	7.170%	$141.2286	$141.23	$141.25	$141.20
Purchase #7	$42.49	6.673%	$45.3254	$45.33	$45.35	$45.30
7 purchase totals =	$1,077.49		$1,137.6040	$1,137.61	$1,137.70	$1,137.40