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	$93.38	8.352%	$101.1791	$101.18	$101.20	$101.20
Purchase #2	$57.99	8.445%	$62.8873	$62.89	$62.90	$62.90
Purchase #3	$99.49	7.698%	$107.1487	$107.15	$107.15	$107.10
Purchase #4	$196.88	4.384%	$205.5112	$205.51	$205.50	$205.50
Purchase #5	$120.58	5.632%	$127.3711	$127.37	$127.35	$127.40
Purchase #6	$145.59	3.359%	$150.4804	$150.48	$150.50	$150.50
Purchase #7	$246.73	12.340%	$277.1765	$277.18	$277.20	$277.20
7 purchase totals =	$960.64		$1,031.7543	$1,031.76	$1,031.80	$1,031.80