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	$73.83	11.395%	$82.2429	$82.24	$82.25	$82.20
Purchase #2	$188.41	13.138%	$213.1633	$213.16	$213.15	$213.20
Purchase #3	$182.50	6.365%	$194.1161	$194.12	$194.10	$194.10
Purchase #4	$197.44	10.444%	$218.0606	$218.06	$218.05	$218.10
Purchase #5	$86.28	3.599%	$89.3852	$89.39	$89.40	$89.40
Purchase #6	$66.97	10.514%	$74.0112	$74.01	$74.00	$74.00
Purchase #7	$134.51	3.720%	$139.5138	$139.51	$139.50	$139.50
7 purchase totals =	$929.94		$1,010.4931	$1,010.49	$1,010.45	$1,010.50