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	$192.85	8.489%	$209.221	$209.22	$209.20	$209.20
Purchase #2	$42.37	10.582%	$46.8536	$46.85	$46.85	$46.90
Purchase #3	$42.32	7.360%	$45.4348	$45.43	$45.45	$45.40
Purchase #4	$222.51	5.793%	$235.4	$235.40	$235.40	$235.40
Purchase #5	$79.75	13.402%	$90.4381	$90.44	$90.45	$90.40
Purchase #6	$163.63	10.699%	$181.1368	$181.14	$181.15	$181.10
Purchase #7	$198.91	5.580%	$210.0092	$210.01	$210.00	$210.00
7 purchase totals =	$942.34		$1,018.4935	$1,018.49	$1,018.50	$1,018.40