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	$106.51	4.706%	$111.5224	$111.52	$111.50	$111.50
Purchase #2	$149.60	4.638%	$156.5384	$156.54	$156.55	$156.50
Purchase #3	$16.68	10.387%	$18.4126	$18.41	$18.40	$18.40
Purchase #4	$86.29	4.448%	$90.1282	$90.13	$90.15	$90.10
Purchase #5	$75.78	13.332%	$85.883	$85.88	$85.90	$85.90
Purchase #6	$219.74	13.276%	$248.9127	$248.91	$248.90	$248.90
Purchase #7	$165.28	7.790%	$178.1553	$178.16	$178.15	$178.20
7 purchase totals =	$819.88		$889.5526	$889.55	$889.55	$889.50