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	$189.66	3.601%	$196.4897	$196.49	$196.50	$196.50
Purchase #2	$52.82	6.281%	$56.1376	$56.14	$56.15	$56.10
Purchase #3	$92.78	12.693%	$104.5566	$104.56	$104.55	$104.60
Purchase #4	$245.57	11.355%	$273.4545	$273.45	$273.45	$273.50
Purchase #5	$41.72	3.351%	$43.118	$43.12	$43.10	$43.10
Purchase #6	$187.50	13.857%	$213.4819	$213.48	$213.50	$213.50
Purchase #7	$81.93	7.451%	$88.0346	$88.03	$88.05	$88.00
7 purchase totals =	$891.98		$975.2729	$975.27	$975.30	$975.30