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	$79.88	7.319%	$85.7264	$85.73	$85.75	$85.70
Purchase #2	$168.69	3.623%	$174.8016	$174.80	$174.80	$174.80
Purchase #3	$80.30	11.678%	$89.6774	$89.68	$89.70	$89.70
Purchase #4	$227.90	11.174%	$253.3655	$253.37	$253.35	$253.40
Purchase #5	$154.52	9.443%	$169.1113	$169.11	$169.10	$169.10
Purchase #6	$178.54	4.789%	$187.0903	$187.09	$187.10	$187.10
Purchase #7	$18.27	12.626%	$20.5768	$20.58	$20.60	$20.60
7 purchase totals =	$908.10		$980.3493	$980.36	$980.40	$980.40