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	$192.80	3.126%	$198.8269	$198.83	$198.85	$198.80
Purchase #2	$136.76	4.410%	$142.7911	$142.79	$142.80	$142.80
Purchase #3	$233.93	11.568%	$260.991	$260.99	$261.00	$261.00
Purchase #4	$58.36	7.176%	$62.5479	$62.55	$62.55	$62.50
Purchase #5	$235.69	12.232%	$264.5196	$264.52	$264.50	$264.50
Purchase #6	$98.46	7.551%	$105.8947	$105.89	$105.90	$105.90
Purchase #7	$116.57	12.611%	$131.2706	$131.27	$131.25	$131.30
7 purchase totals =	$1,072.57		$1,166.8418	$1,166.84	$1,166.85	$1,166.80