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	$190.88	5.861%	$202.0675	$202.07	$202.05	$202.10
Purchase #2	$41.35	8.328%	$44.7936	$44.79	$44.80	$44.80
Purchase #3	$189.31	3.546%	$196.0229	$196.02	$196.00	$196.00
Purchase #4	$34.67	10.255%	$38.2254	$38.23	$38.25	$38.20
Purchase #5	$175.37	6.143%	$186.143	$186.14	$186.15	$186.10
Purchase #6	$90.48	10.709%	$100.1695	$100.17	$100.15	$100.20
Purchase #7	$12.45	11.758%	$13.9139	$13.91	$13.90	$13.90
7 purchase totals =	$734.51		$781.3358	$781.33	$781.30	$781.30