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	$85.30	13.622%	$96.9196	$96.92	$96.90	$96.90
Purchase #2	$165.76	4.610%	$173.4015	$173.40	$173.40	$173.40
Purchase #3	$80.44	10.870%	$89.1838	$89.18	$89.20	$89.20
Purchase #4	$86.47	12.654%	$97.4119	$97.41	$97.40	$97.40
Purchase #5	$41.48	6.811%	$44.3052	$44.31	$44.30	$44.30
Purchase #6	$98.45	5.190%	$103.5596	$103.56	$103.55	$103.60
Purchase #7	$161.68	11.567%	$180.3815	$180.38	$180.40	$180.40
7 purchase totals =	$719.58		$785.1631	$785.16	$785.15	$785.20