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	$160.67	6.550%	$171.1939	$171.19	$171.20	$171.20
Purchase #2	$84.64	6.391%	$90.0493	$90.05	$90.05	$90.00
Purchase #3	$191.72	3.736%	$198.8827	$198.88	$198.90	$198.90
Purchase #4	$182.85	7.400%	$196.3809	$196.38	$196.40	$196.40
Purchase #5	$113.92	10.663%	$126.0673	$126.07	$126.05	$126.10
Purchase #6	$116.25	13.158%	$131.5462	$131.55	$131.55	$131.50
Purchase #7	$124.74	9.119%	$136.115	$136.12	$136.10	$136.10
7 purchase totals =	$974.79		$1,050.2353	$1,050.24	$1,050.25	$1,050.20