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	$187.25	3.731%	$194.2363	$194.24	$194.25	$194.20
Purchase #2	$54.67	5.570%	$57.7151	$57.72	$57.70	$57.70
Purchase #3	$61.30	8.235%	$66.3481	$66.35	$66.35	$66.30
Purchase #4	$65.86	12.512%	$74.1004	$74.10	$74.10	$74.10
Purchase #5	$182.98	7.346%	$196.4217	$196.42	$196.40	$196.40
Purchase #6	$181.31	3.870%	$188.3267	$188.33	$188.35	$188.30
Purchase #7	$23.46	9.853%	$25.7715	$25.77	$25.75	$25.80
7 purchase totals =	$756.83		$802.9198	$802.93	$802.90	$802.80