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	$103.64	10.695%	$114.7243	$114.72	$114.70	$114.70
Purchase #2	$33.83	6.755%	$36.1152	$36.12	$36.10	$36.10
Purchase #3	$115.62	13.665%	$131.4195	$131.42	$131.40	$131.40
Purchase #4	$243.62	7.538%	$261.9841	$261.98	$262.00	$262.00
Purchase #5	$96.71	5.521%	$102.0494	$102.05	$102.05	$102.00
Purchase #6	$7.89	3.457%	$8.1628	$8.16	$8.15	$8.20
Purchase #7	$127.42	13.871%	$145.0944	$145.09	$145.10	$145.10
7 purchase totals =	$728.73		$799.5497	$799.54	$799.50	$799.50