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	$82.83	10.512%	$91.5371	$91.54	$91.55	$91.50
Purchase #2	$86.73	5.522%	$91.5192	$91.52	$91.50	$91.50
Purchase #3	$204.74	11.119%	$227.505	$227.51	$227.50	$227.50
Purchase #4	$48.46	13.165%	$54.8398	$54.84	$54.85	$54.80
Purchase #5	$103.91	6.143%	$110.2932	$110.29	$110.30	$110.30
Purchase #6	$7.67	7.715%	$8.2617	$8.26	$8.25	$8.30
Purchase #7	$162.69	8.737%	$176.9042	$176.90	$176.90	$176.90
7 purchase totals =	$697.03		$760.8602	$760.86	$760.85	$760.80