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	$245.71	9.454%	$268.9394	$268.94	$268.95	$268.90
Purchase #2	$145.83	3.152%	$150.4266	$150.43	$150.45	$150.40
Purchase #3	$98.88	12.705%	$111.4427	$111.44	$111.45	$111.40
Purchase #4	$67.89	6.286%	$72.1576	$72.16	$72.15	$72.20
Purchase #5	$83.50	4.605%	$87.3452	$87.35	$87.35	$87.30
Purchase #6	$187.27	4.810%	$196.2777	$196.28	$196.30	$196.30
Purchase #7	$125.44	3.813%	$130.223	$130.22	$130.20	$130.20
7 purchase totals =	$954.52		$1,016.8122	$1,016.82	$1,016.85	$1,016.70