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	$11.42	5.766%	$12.0785	$12.08	$12.10	$12.10
Purchase #2	$67.93	9.329%	$74.2672	$74.27	$74.25	$74.30
Purchase #3	$131.61	8.594%	$142.9206	$142.92	$142.90	$142.90
Purchase #4	$79.48	7.295%	$85.2781	$85.28	$85.30	$85.30
Purchase #5	$165.88	8.705%	$180.3199	$180.32	$180.30	$180.30
Purchase #6	$207.42	12.421%	$233.1836	$233.18	$233.20	$233.20
Purchase #7	$47.86	10.572%	$52.9198	$52.92	$52.90	$52.90
7 purchase totals =	$711.60		$780.9677	$780.97	$780.95	$781.00