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	$145.98	8.619%	$158.562	$158.56	$158.55	$158.60
Purchase #2	$148.41	6.803%	$158.5063	$158.51	$158.50	$158.50
Purchase #3	$7.81	8.185%	$8.4492	$8.45	$8.45	$8.40
Purchase #4	$200.89	4.270%	$209.468	$209.47	$209.45	$209.50
Purchase #5	$145.54	11.751%	$162.6424	$162.64	$162.65	$162.60
Purchase #6	$159.83	10.685%	$176.9078	$176.91	$176.90	$176.90
Purchase #7	$79.76	7.704%	$85.9047	$85.90	$85.90	$85.90
7 purchase totals =	$888.22		$960.4404	$960.44	$960.40	$960.40