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	$88.69	10.558%	$98.0539	$98.05	$98.05	$98.10
Purchase #2	$80.72	5.838%	$85.4324	$85.43	$85.45	$85.40
Purchase #3	$130.69	6.713%	$139.4632	$139.46	$139.45	$139.50
Purchase #4	$198.42	11.441%	$221.1212	$221.12	$221.10	$221.10
Purchase #5	$42.83	4.656%	$44.8242	$44.82	$44.80	$44.80
Purchase #6	$109.34	5.372%	$115.2137	$115.21	$115.20	$115.20
Purchase #7	$6.96	5.331%	$7.331	$7.33	$7.35	$7.30
7 purchase totals =	$657.65		$711.4396	$711.42	$711.40	$711.40