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	$16.87	13.691%	$19.1797	$19.18	$19.20	$19.20
Purchase #2	$232.27	7.432%	$249.5323	$249.53	$249.55	$249.50
Purchase #3	$93.78	11.684%	$104.7373	$104.74	$104.75	$104.70
Purchase #4	$234.72	5.648%	$247.977	$247.98	$248.00	$248.00
Purchase #5	$75.88	13.441%	$86.079	$86.08	$86.10	$86.10
Purchase #6	$200.76	10.672%	$222.1851	$222.19	$222.20	$222.20
Purchase #7	$127.28	3.158%	$131.2995	$131.30	$131.30	$131.30
7 purchase totals =	$981.56		$1,060.9899	$1,061.00	$1,061.10	$1,061.00