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	$64.89	3.485%	$67.1514	$67.15	$67.15	$67.20
Purchase #2	$192.30	4.213%	$200.4016	$200.40	$200.40	$200.40
Purchase #3	$43.31	5.600%	$45.7354	$45.74	$45.75	$45.70
Purchase #4	$158.74	10.174%	$174.8902	$174.89	$174.90	$174.90
Purchase #5	$194.66	5.472%	$205.3118	$205.31	$205.30	$205.30
Purchase #6	$113.28	6.637%	$120.7984	$120.80	$120.80	$120.80
Purchase #7	$178.61	11.345%	$198.8733	$198.87	$198.85	$198.90
7 purchase totals =	$945.79		$1,013.1621	$1,013.16	$1,013.15	$1,013.20