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	$205.68	6.209%	$218.4507	$218.45	$218.45	$218.50
Purchase #2	$76.36	4.114%	$79.5015	$79.50	$79.50	$79.50
Purchase #3	$185.48	10.144%	$204.2951	$204.30	$204.30	$204.30
Purchase #4	$80.54	5.735%	$85.159	$85.16	$85.15	$85.20
Purchase #5	$91.36	13.218%	$103.436	$103.44	$103.45	$103.40
Purchase #6	$232.34	7.814%	$250.495	$250.50	$250.50	$250.50
Purchase #7	$118.79	13.308%	$134.5986	$134.60	$134.60	$134.60
7 purchase totals =	$990.55		$1,075.9359	$1,075.95	$1,075.95	$1,076.00