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	$51.63	8.399%	$55.9664	$55.97	$55.95	$56.00
Purchase #2	$9.29	12.608%	$10.4613	$10.46	$10.45	$10.50
Purchase #3	$215.82	10.435%	$238.3408	$238.34	$238.35	$238.30
Purchase #4	$166.89	8.179%	$180.5399	$180.54	$180.55	$180.50
Purchase #5	$135.96	12.477%	$152.9237	$152.92	$152.90	$152.90
Purchase #6	$166.50	13.131%	$188.3631	$188.36	$188.35	$188.40
Purchase #7	$210.82	5.453%	$222.316	$222.32	$222.30	$222.30
7 purchase totals =	$956.91		$1,048.9112	$1,048.91	$1,048.85	$1,048.90