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	$175.52	9.318%	$191.875	$191.88	$191.90	$191.90
Purchase #2	$242.35	3.276%	$250.2894	$250.29	$250.30	$250.30
Purchase #3	$6.58	9.859%	$7.2287	$7.23	$7.25	$7.20
Purchase #4	$129.51	12.648%	$145.8904	$145.89	$145.90	$145.90
Purchase #5	$173.62	3.682%	$180.0127	$180.01	$180.00	$180.00
Purchase #6	$183.28	9.365%	$200.4442	$200.44	$200.45	$200.40
Purchase #7	$187.41	4.749%	$196.3101	$196.31	$196.30	$196.30
7 purchase totals =	$1,098.27		$1,172.0505	$1,172.05	$1,172.10	$1,172.00