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	$113.60	8.477%	$123.2299	$123.23	$123.25	$123.20
Purchase #2	$119.68	6.736%	$127.7416	$127.74	$127.75	$127.70
Purchase #3	$124.81	5.276%	$131.395	$131.40	$131.40	$131.40
Purchase #4	$69.67	5.549%	$73.536	$73.54	$73.55	$73.50
Purchase #5	$73.96	11.857%	$82.7294	$82.73	$82.75	$82.70
Purchase #6	$113.97	10.589%	$126.0383	$126.04	$126.05	$126.00
Purchase #7	$70.52	11.471%	$78.6093	$78.61	$78.60	$78.60
7 purchase totals =	$686.21		$743.2795	$743.29	$743.35	$743.10