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	$189.47	13.623%	$215.2815	$215.28	$215.30	$215.30
Purchase #2	$188.73	7.623%	$203.1169	$203.12	$203.10	$203.10
Purchase #3	$215.40	4.353%	$224.7764	$224.78	$224.80	$224.80
Purchase #4	$47.62	7.819%	$51.3434	$51.34	$51.35	$51.30
Purchase #5	$79.50	13.422%	$90.1705	$90.17	$90.15	$90.20
Purchase #6	$178.61	7.449%	$191.9147	$191.91	$191.90	$191.90
Purchase #7	$91.51	7.535%	$98.4053	$98.41	$98.40	$98.40
7 purchase totals =	$990.84		$1,075.0087	$1,075.01	$1,075.00	$1,075.00