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	$14.48	8.250%	$15.6746	$15.67	$15.65	$15.70
Purchase #2	$99.79	12.801%	$112.5641	$112.56	$112.55	$112.60
Purchase #3	$179.49	6.691%	$191.4997	$191.50	$191.50	$191.50
Purchase #4	$221.51	6.263%	$235.3832	$235.38	$235.40	$235.40
Purchase #5	$146.57	12.203%	$164.4559	$164.46	$164.45	$164.50
Purchase #6	$6.84	9.361%	$7.4803	$7.48	$7.50	$7.50
Purchase #7	$171.28	5.247%	$180.2671	$180.27	$180.25	$180.30
7 purchase totals =	$839.96		$907.3249	$907.32	$907.30	$907.50