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	$176.84	13.368%	$200.48	$200.48	$200.50	$200.50
Purchase #2	$99.50	12.133%	$111.5723	$111.57	$111.55	$111.60
Purchase #3	$94.96	3.736%	$98.5077	$98.51	$98.50	$98.50
Purchase #4	$216.49	3.459%	$223.9784	$223.98	$224.00	$224.00
Purchase #5	$186.93	7.297%	$200.5703	$200.57	$200.55	$200.60
Purchase #6	$107.33	3.223%	$110.7892	$110.79	$110.80	$110.80
Purchase #7	$158.33	13.332%	$179.4386	$179.44	$179.45	$179.40
7 purchase totals =	$1,040.38		$1,125.3365	$1,125.34	$1,125.35	$1,125.40