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	$174.88	5.401%	$184.3253	$184.33	$184.35	$184.30
Purchase #2	$166.86	9.154%	$182.1344	$182.13	$182.15	$182.10
Purchase #3	$82.89	3.708%	$85.9636	$85.96	$85.95	$86.00
Purchase #4	$49.63	12.716%	$55.941	$55.94	$55.95	$55.90
Purchase #5	$22.60	6.650%	$24.1029	$24.10	$24.10	$24.10
Purchase #6	$41.44	10.749%	$45.8944	$45.89	$45.90	$45.90
Purchase #7	$41.96	12.265%	$47.1064	$47.11	$47.10	$47.10
7 purchase totals =	$580.26		$625.4680	$625.46	$625.50	$625.40