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	$217.88	13.585%	$247.479	$247.48	$247.50	$247.50
Purchase #2	$160.30	6.786%	$171.178	$171.18	$171.20	$171.20
Purchase #3	$159.34	10.378%	$175.8763	$175.88	$175.90	$175.90
Purchase #4	$219.30	8.611%	$238.1839	$238.18	$238.20	$238.20
Purchase #5	$94.73	5.469%	$99.9108	$99.91	$99.90	$99.90
Purchase #6	$145.55	11.539%	$162.345	$162.35	$162.35	$162.30
Purchase #7	$63.46	3.862%	$65.9108	$65.91	$65.90	$65.90
7 purchase totals =	$1,060.56		$1,160.8838	$1,160.89	$1,160.95	$1,160.90