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	$94.51	5.561%	$99.7657	$99.77	$99.75	$99.80
Purchase #2	$197.28	10.534%	$218.0615	$218.06	$218.05	$218.10
Purchase #3	$51.72	4.173%	$53.8783	$53.88	$53.90	$53.90
Purchase #4	$118.64	10.716%	$131.3535	$131.35	$131.35	$131.40
Purchase #5	$218.25	7.181%	$233.9225	$233.92	$233.90	$233.90
Purchase #6	$246.58	6.296%	$262.1047	$262.10	$262.10	$262.10
Purchase #7	$12.72	8.586%	$13.8121	$13.81	$13.80	$13.80
7 purchase totals =	$939.70		$1,012.8983	$1,012.89	$1,012.85	$1,013.00