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	$184.68	7.449%	$198.4368	$198.44	$198.45	$198.40
Purchase #2	$115.50	13.841%	$131.4864	$131.49	$131.50	$131.50
Purchase #3	$196.57	10.216%	$216.6516	$216.65	$216.65	$216.70
Purchase #4	$47.91	8.488%	$51.9766	$51.98	$52.00	$52.00
Purchase #5	$194.61	8.391%	$210.9397	$210.94	$210.95	$210.90
Purchase #6	$164.92	3.398%	$170.524	$170.52	$170.50	$170.50
Purchase #7	$81.97	4.131%	$85.3562	$85.36	$85.35	$85.40
7 purchase totals =	$986.16		$1,065.3713	$1,065.38	$1,065.40	$1,065.40