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	$200.48	9.529%	$219.5837	$219.58	$219.60	$219.60
Purchase #2	$216.43	7.804%	$233.3202	$233.32	$233.30	$233.30
Purchase #3	$138.58	7.236%	$148.6076	$148.61	$148.60	$148.60
Purchase #4	$150.45	10.393%	$166.0863	$166.09	$166.10	$166.10
Purchase #5	$80.47	11.237%	$89.5124	$89.51	$89.50	$89.50
Purchase #6	$114.32	10.142%	$125.9143	$125.91	$125.90	$125.90
Purchase #7	$205.74	4.631%	$215.2678	$215.27	$215.25	$215.30
7 purchase totals =	$1,106.47		$1,198.2923	$1,198.29	$1,198.25	$1,198.30