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	$179.93	9.272%	$196.6131	$196.61	$196.60	$196.60
Purchase #2	$173.40	7.754%	$186.8454	$186.85	$186.85	$186.80
Purchase #3	$54.49	4.679%	$57.0396	$57.04	$57.05	$57.00
Purchase #4	$170.36	10.186%	$187.7129	$187.71	$187.70	$187.70
Purchase #5	$101.58	9.538%	$111.2687	$111.27	$111.25	$111.30
Purchase #6	$149.50	13.614%	$169.8529	$169.85	$169.85	$169.90
Purchase #7	$45.69	4.536%	$47.7625	$47.76	$47.75	$47.80
7 purchase totals =	$874.95		$957.0951	$957.09	$957.05	$957.10