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	$143.33	7.452%	$154.011	$154.01	$154.00	$154.00
Purchase #2	$167.40	10.663%	$185.2499	$185.25	$185.25	$185.20
Purchase #3	$65.82	12.836%	$74.2687	$74.27	$74.25	$74.30
Purchase #4	$12.31	7.157%	$13.191	$13.19	$13.20	$13.20
Purchase #5	$71.56	13.328%	$81.0975	$81.10	$81.10	$81.10
Purchase #6	$115.37	3.189%	$119.0491	$119.05	$119.05	$119.00
Purchase #7	$39.74	7.843%	$42.8568	$42.86	$42.85	$42.90
7 purchase totals =	$615.53		$669.7240	$669.73	$669.70	$669.70