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	$71.48	6.442%	$76.0847	$76.08	$76.10	$76.10
Purchase #2	$176.26	11.700%	$196.8824	$196.88	$196.90	$196.90
Purchase #3	$123.61	10.207%	$136.2269	$136.23	$136.25	$136.20
Purchase #4	$176.79	9.753%	$194.0323	$194.03	$194.05	$194.00
Purchase #5	$133.74	8.653%	$145.3125	$145.31	$145.30	$145.30
Purchase #6	$213.41	11.633%	$238.236	$238.24	$238.25	$238.20
Purchase #7	$101.47	4.870%	$106.4116	$106.41	$106.40	$106.40
7 purchase totals =	$996.76		$1,093.1864	$1,093.18	$1,093.25	$1,093.10