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	$210.55	6.109%	$223.4125	$223.41	$223.40	$223.40
Purchase #2	$54.91	13.197%	$62.1565	$62.16	$62.15	$62.20
Purchase #3	$127.70	3.195%	$131.78	$131.78	$131.80	$131.80
Purchase #4	$17.45	3.338%	$18.0325	$18.03	$18.05	$18.00
Purchase #5	$195.46	13.828%	$222.4882	$222.49	$222.50	$222.50
Purchase #6	$224.76	9.359%	$245.7953	$245.80	$245.80	$245.80
Purchase #7	$189.88	12.727%	$214.046	$214.05	$214.05	$214.00
7 purchase totals =	$1,020.71		$1,117.7110	$1,117.72	$1,117.75	$1,117.70